What does the word cocker mean in British and American English? I only know it from cocker spaniel and as a last name, as in Joe Cocker.
British slang can be unintelligible to me. Sure, I’m familiar with the old standbys such as, “Wanker”, “Bollocks”, etc, but some I hear for the first time in movies and really don’t know what to make of them.
They’re hunting dogs - the name is thought to derive from them being used to flush birds (such as woodcock) out of the undergrowth.
Cocker isn’t really a word in common parlance apart from the name of the dog. You could instead have:
Cock up = embarrassing mistake (‘cock’ perhaps meaning to tilt or skew here, although it is also a slang term for penis, and quite an old one, so maybe that)
Googling “cocker british slang” says
In British slang, “cocker” is an informal term for a mate or friend. It’s often used in the phrase “old cocker”.
Doesn’t even have to be British. Hell, generational American slang would be completely unintelligible to be if I didn’t have a couple pre-teens in my house. Gen Alpha slang is [i]weird[/] (though fun and playful.) Any culture you don’t keep up on will have its own language that seems impenetrable.
If I heard the word “cocker” the first thing that comes to mind is “alter kocker,” the Yiddish phrase for an old man, aka “old fart.” Don’t think I’ve ever heard that word in any other usage.
Are you sure it’s “alter Kocker” and not “alter Knacker”? Because that’s the German expression for old fart, and Yiddish and German are closely related.
I have no children, but I work in an educational environment full of kids, so I hear all the latest lingo. LOL
Definitely. It’s kocker/cocker/kaker in the US.
This is a little niche, but:
The term “cocked hat” (a three-rail shot into a side pocket) must’ve originated with British snooker players (another link from The Commonwealth). You’ll sometimes see references to the “cocked hat” in American pocket-pool instructional books & videos, the American readers of which perhaps learn the unfamiliar term by rote.
I wonder if this has anything to do with the niche/regional (?) American English expression “fart knocker”?
It took me a long time to grok, in “The Lumberjack Song” the line
Suspendies and a bra
I mean I understood what was being said from the context but it conjured an extremely odd picture in my mind.
In Welsh English, “cock” can be more or less “friend / buddy” (as can “butt,” which is rather more common). I don’t think I’ve heard “cock” used that way more than once or twice, but it was definitely jarring.
Chip butties are also definitely a thing (cut up a bap, fill with chips, eat). I can’t think of an American equivalent.
o what do British use for id with picture?
I believe it relates to old-fashioned guns - if “cocked”, they were ready to fire, so a “cock up” was what happened when you didn’t mean to fire it - but did.
San Diegans shove fries into a burrito and have the audacity to call it a “California burrito” despite it not being well known in the northern 9/10ths or more of the state.
I was born and raised in San Diego, and I have never seen this. Not doubting you, just saying that it wasn’t widespread in the 20th century.
They’re known in the part that counts. 
It isn’t just the fries. “California style” is a much more pared down burrito than the overstuffed “Mission” monsters. Just carne asada, fries, cheese and pico or guac.
What the hell is a “bap?”
A soft disc-shaped bread roll.
Also sometimes a slang word for breasts, which is why the British Association of Plastic Surgeons changed their name, supposedly
Oh, yeah, I forgot all about that - I think that’s estuary slang - I wonder if it’s related to ‘me old cock sparrer’ (cock sparrow).
I think cocked hat originated with navigating on paper maps - when you triangulate three bearings, they seldom meet at an exact point (your location), but instead cross to form a (hopefully) small triangle - known as a ‘cocked hat’ (with your location falling inside or near the outside of this triangle).
https://discovery.ucl.ac.uk/id/eprint/10129645/1/Barany_CockHatJNav.pdf