Q From Dr Martin Taylor: Is there an interesting derivation of the phrase, peter out?
A There probably is, but we’re not sure. Though its sense — of something that decreases or fades gradually before coming to an end — is well enough known, its origin is puzzling, and most reference works just say they don’t know what it is.
A clue to where it comes from lies in this comment in an article on hard-rock mining in Appleton’s Journal of New York, dated 18 October 1873: “No mortal forecast can tell whether a good vein will not narrow to nothing (‘peter out,’ as the miners phrase it) in a week; and, on the other hand, it may widen in that time beyond all anticipation”. Other evidence backs up the implication here that the phrase began its life as a bit of American miner’s jargon for exhausted veins of ore. The first example in the Oxford English Dictionary is from 1846 (so before the California gold rush that some have suggested as its source). Taking it back further, though, requires some guesswork.
We should leave aside a derivation from the proper name, which is often given as a source, especially in reference to St Peter, whose support for Jesus waned at a crucial moment. But this is unlikely to be the origin, since there is no direct evidence for the link, and it seems somewhat strained as an association of ideas.
There are two main possibilities for where it came from. One is the saltpetre (US spelling saltpeter) that was a component of the blasting power that miners used (the second part comes from Greek petros, a rock, which by an odd link is also the source of St Peter’s name); this sounds a bit of a stretch, but you never know. The other is French péter, to fart, which famously appears in the English petard for a medieval military explosive device, from which we get “hoist by his own petard”.
There are other slang expressions that suggest the second may be the more likely origin. Peter was used in the eighteenth century for a kind of loaded dice (on which, as Jonathon Green explains it, the loser was hoist, as by a petard). It also turns up about the start of the nineteenth century as a slang verb meaning to stop or cease (there’s an example known from 1812), which also looks as though it derives from French.
However, at this point the evidence ... ahem ... peters out, so nobody really knows.