If something chaps your ass, it irritates you intensely. The phrase is American and informal, and it is usually aimed at a persistent, nagging annoyance rather than a single outrage: a colleague’s habit, a rule that makes no sense, a driver who never indicates. Politer company gets the softened forms ‘that chaps my hide’ or ‘chaps my butt’, which carry the same feeling with less sting.
What’s the origin of the phrase ‘chaps my ass’?
The verb is far older than the phrase. To chap has meant to split or crack open in fissures since Middle English, recorded from the mid fifteenth century and usually describing what cold and wind do to exposed skin. The noun, a chap as a crack in the skin, is older still, from the late fourteenth century. The word is probably a relative of chop, perhaps via Middle Dutch kappen, to cut. That literal sense survives in everyday English in chapped lips and chapped hands, which is why the lip balm is called ChapStick.
The figurative leap is not hard to follow. Skin chaps where it is rubbed raw, so something that chaps your ass is wearing you down by constant friction. The phrase is often assumed to be cowboy talk, a memory of long days in the saddle, and the leather riding leggings called chaps encourage that association. The imagery fits, but the expression needs nothing more than the ordinary English verb, and no early citation has surfaced to tie it to ranching in particular.
Hard documentation is in fact thin all round. Green’s Dictionary of Slang records ‘chap someone’s ass’ as slang for to annoy or irritate, and separately notes a related American student usage from the late 1990s in which something that ‘chapped’ was simply bad or displeasing. But no convincing first printing of ‘chaps my ass’ has been produced, so the honest dating is a vague one: it belongs to twentieth century American speech and settled into wide use in the second half of the century.
When readers raised the question on this site’s bulletin board in 2004, one suggested the breaking in of new saddles, while another pointed out that plenty of people with no saddle experience used the phrase, offering the earthier variant ‘chaffs the crack of my ass’. That is probably the right emphasis: friction, not horsemanship, is the living image. The gentler ‘chaps my hide’ is the standard euphemism, and jokey substitutions like ‘chaps my khakis’ turn up too. As with ‘gets my goat’, the phrase is understood by everyone and pinned down by no one.