# The glass you only break in case of fire: this and other switch guards is a "Mollyguard?" Etymology? **URL:** \ **Category:** Factual Questions\ **Created:** [August 16, 2016, 1:49am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971 "2016-08-16T01:49:46Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 16, 2016, 1:49am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/1 "2016-08-16T01:49:46Z")
I read “Mollyguard” (in Wiki, “kill switch”) as specifically “the shielding thing you flip up or otherwise overcome to get at the real big button that is super powerful” which comprised the glass you’re supposed to beak to get at the whatever. Arming switches for weapons in jet fighters–many of them too are protected by a “are you sure you want to get at this switch to flip it” cover. Has anyone besides wiki ever heard them called Mollyguards? And where does that word com from? Who was Molly? ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [August 16, 2016, 2:23am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/2 "2016-08-16T02:23:45Z")
I’ve operated equipment with them, but never heard of them called that. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [August 16, 2016, 2:29am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/3 "2016-08-16T02:29:31Z")
I first heard the term several years ago. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [August 16, 2016, 2:52am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/4 "2016-08-16T02:52:30Z")
If this is correct, she was a [programmer’s daughter.](https://en.wiktionary.org/wiki/molly-guard) Probably unrelated to [molly bolts,](https://en.wikipedia.org/wiki/Molly_(fastener)) however they may have been intended to keep out [gun molls.](https://en.wikipedia.org/wiki/Gun_moll) ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [August 16, 2016, 2:59am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/5 "2016-08-16T02:59:50Z")
In a glossary of computer jargon that goes back at least a couple decades is [this entry](http://www.catb.org/jargon/html/M/molly-guard.html): > [@](#): > > molly-guard: /mol�ee�gard/, n. > > [University of Illinois] A shield to prevent tripping of some Big Red Switch by clumsy or ignorant hands. Originally used of the plexiglass covers improvised for the BRS on an IBM 4341 after a programmer’s toddler daughter (named Molly) frobbed it twice in one day. Later generalized to covers over stop/reset switches on disk drives and networking equipment. In hardware catalogues, you’ll see the much less interesting description “guarded button”. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 16, 2016, 3:34am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/6 "2016-08-16T03:34:09Z")
Huh. I was looking for my local F16 circuit board layout, but did come up with this: under “switches” (tons of 'em!) in a catalog for airplane people, they’re separately listed as “switch guards/covers”: > **[Switch Guards/Covers | Aircraft Spruce](https://www.aircraftspruce.com/categories/aircraft_parts/ap/menus/el/switches_zaccessories.html)** > > Aircraft Spruce is a worldwide distributor of certified and homebuilt aircraft supplies. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 16, 2016, 3:36am UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/7 "2016-08-16T03:36:24Z")
> [@Robot\_Arm](#): > > In a glossary of computer jargon that goes back at least a couple decades … Wow, I haven’t seen that file in years and years! I thought by now it would have been deprecated. ETA: not a snark at quality of cite, which is primo; just a note on modern lexicography. ---
**Author:** ![That\_Don\_Guy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/that_don_guy/32/538_2.png) [@That\_Don\_Guy](https://boards.straightdope.com/u/That_Don_Guy)\ **Post date:** [August 16, 2016, 2:07pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/8 "2016-08-16T14:07:51Z")
> [@Robot\_Arm](#): > > In a glossary of computer jargon that goes back at least a couple decades is [this entry](http://www.catb.org/jargon/html/M/molly-guard.html): IBM “big iron” computers like the 360 had a rather large button that you pulled out in red with “EMERGENCY STOP” marked on it; I’m not quite sure what its purpose was, but it would shut down the entire computer immediately. This is what the original Molly pulled that led to the “Molly Guard” being installed. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [August 16, 2016, 2:12pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/9 "2016-08-16T14:12:41Z")
Never heard the term before this thread, despite coming up in the tech industry. Having had twins that thought the big, blue-ringed button on the front of CPUs was to be pushed immediately and every time encountered, including in homes and businesses being visited, I would have appreciated it. ---
**Author:** ![Zsofia](https://avatars.discourse-cdn.com/v4/letter/z/7bcc69/32.png) [@Zsofia](https://boards.straightdope.com/u/Zsofia)\ **Post date:** [August 16, 2016, 2:42pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/10 "2016-08-16T14:42:55Z")
I’ve heard of that term but haven’t heard it in years, not sure where I did originally hear it. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [August 16, 2016, 2:45pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/11 "2016-08-16T14:45:58Z")
Most definitely a terminology that needs to be revived. I will refer to them as Mollyguards henceforth. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [August 16, 2016, 3:00pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/12 "2016-08-16T15:00:23Z")
Since my 3 year old grandson has just started turning every switch in the house on, I’m calling them Marcusguards. Dennis ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [August 16, 2016, 3:08pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/13 "2016-08-16T15:08:44Z")
What would be particularly cool would be to track down Molly. One would guess she would be in her 50’s by now. But given the apparent history of the term finding her should not actually be all that hard. It is likely she knows her special place in the world. Finding people that relate to terms like this is a rather nice and rare thing. ---
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [August 16, 2016, 4:43pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/14 "2016-08-16T16:43:23Z")
The Jargon File dates back to 1975. The story may be older, so she could be in her 70s or 80s. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [August 16, 2016, 5:02pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/15 "2016-08-16T17:02:06Z")
> [@BrotherCadfael](#): > > The Jargon File dates back to 1975. The story may be older, so she could be in her 70s or 80s. The Jargon File was under continuous revision through the 80s and 90s, and updated periodically even into the Naughties. (Maybe even this decade; I haven’t really checked the rev history lately.) And the [specific machine mentioned](https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP4341.html) in the anecdote was introduced to the market in 1979, so that’s the EARLIEST that little Molly could have been a toddler. She’d be late-thirties, early-fourties. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [August 16, 2016, 6:12pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/16 "2016-08-16T18:12:24Z")
Eric Raymond basically took ownership of the Jargon File in the 1990s, and he updates it every so often; you can find original ITS-era (that is, 1970s through mid-1980s) files online in various places, but the ITS culture collapsed when the PDP-10 series of mainframe computers was killed off without a successor in the 1980s and the cultural changes of the era made the file obsolete rather quickly after that. Raymond took over the file once the AI Lab was gone and the File’s original owners scattered. [This is a 1988 version, one of the last from the original source, the PDP-10 computer running ITS at MIT’s AI Lab.](http://www.dourish.com/goodies/jargon.html) ---
**Author:** ![Bert\_Nobbins](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@Bert\_Nobbins](https://boards.straightdope.com/u/Bert_Nobbins)\ **Post date:** [August 16, 2016, 6:19pm UTC](https://boards.straightdope.com/t/the-glass-you-only-break-in-case-of-fire-this-and-other-switch-guards-is-a-mollyguard-etymology/762971/17 "2016-08-16T18:19:09Z")
> [@That\_Don\_Guy](#): > > IBM “big iron” computers like the 360 had a rather large button that you pulled out in red with “EMERGENCY STOP” marked on it; I’m not quite sure what its purpose was, but it would shut down the entire computer immediately. This is what the original Molly pulled that led to the “Molly Guard” being installed. The IBM 1130 at Cambridge University Engineering Dept had a similiar pull-switch, though IIRC it was labelled EMERGENCY PULL. The emergency in question was the computer catching fire. I was told that pulling it turned off all the power at once by separating multiple connectors, and reconnecting things required the expensive services of an IBM technician for a long time. I don’t recall it having a mollyguard; if you needed it you needed it _fast_. But it was at least 4 feet off the ground and presumably required quite a hefty pull, so I don’t think there was much danger from toddlers. I don’t think it was ever explicity stated, but it was generally held that pulling it for a laugh would get you booted out the university at amazing speed.