Like “does the Pope shit in the woods?” or “that train has sailed?”
Also, what good examples can you think of?
Though this is not for idiomatic phrases, there’s also misnomer, for when something is named in a misleading or inappropriate manner.
Though, different dictionaries seem to give different scope to what can and cannot be considered a misnomer, and others place different emphasis on precisely how the name is wrong qualifies it as a misnomer.
Cambridge lists ‘dry cleaning’ as an example, a process that involves liquid and is thus antithetical.
The focus is on something being named such that the obvious, plain reading of it implies the precise opposite.
Merriam Webster lists that its a misnomer to call a farmer a peasant, which is not antithetical but more along the lines of being rude, out of date.
Their conception of it is fairly broad: any name that is inaccurate for basically any reason, or even just a word that has offensive connotations due to inaccuracy.
Dictionary.com uses the examples of Chinese Checkers, a funny bone, and hay fever.
They focus the definition on the factual/historical inaccuracy of the term:
Chinese Checkers did not originate in China, a funny bone is actually a nerve, not a bone, and hay fever is not caused by hay, nor is it a fever.
Cambridge lists ‘dry cleaning’ as an example, a process that involves liquid and is thus antithetical.
Ehhh…man, I dunno about that example, Cambridge. Like, wouldn’t sweeping involve cleaning something? Vacuuming?
No, but if they’re going to assert that cleaning involves liquid, they would be counterexamples to such an assertion.