This rather silly term is popping up everywhere. I first read it in Douglas Adam’s The Hitchhikers Guide to the Universe - and it could easily be just the kind of silly thing he invented or had picked up some obscure place. At least I always thing of Douglas Adams when I hear “mind-boggling”, but these days it seems to have gone mainstream - even Bloomberg, supposedly a fairly conservative media. So is “mind-boggling” invented or popularized by Douglas Adams, or did it exist and was popular before he started to use it.

Not sure, but I always thought it had some sort of association with the game Boggle.

According to my Oxford Etymological Dictionary, “boggle” goes back to the sixteenth century (they say it means “to start with fright”, though it’s undergone shifts in meaning over the years - it’s from the same root as “bogey”, as in “bogeyman”). I’ve seen “mind-boggling”, “the mind boggles”, and even “it boggles the mind” … I’m pretty sure all of them predate Douglas Adams, but I don’t have examples handy …

The phrase has been around in the English language in general for many years. Someone with access to the OED can give us an idea just how many, I bet. It sure didn’t start with Douglas Adams.

The word boggle came from Celtic, and the original meaning of it means to overcome with fright or astonishment. It seems to be derived from a dialectal variant of bogle ‘a hobgoblin, a bogey’ - from Scots bogill, “perhaps ultimately from Welsh bwg, ghost, hobgoblin.” (cite: American Heritage Dictionary, 4th ed., p. 206.)

In Welsh, the vowel w in bwg is pronounced like u. So bwg rhymes with Shug (name of a character in The Color Purple by Alice Walker). Or maybe the beginning of the word googol.

The British were using the phrases “The imagination boggles” and “the mind boggles” as early as the 1890’s, usually in Philosophy articles. It wasn’t common, but existed. The phrase “mind-boggling” seems to show up in the US and in Britain in the 1950’s.

The OED dates it from 1955:

“Boggle” itself dates from 1598; Shakespeare used it a couple of years later in All’s Well That Ends Well, though it meant “react in fright” back then.

As others have said, and said more intelligently, the latter is the case. U.K. readers/listeners, anyway, would not have foun the phrase novel at all.