mot

mot \moh\, noun:

1. a pithy or witty remark; bon mot.
2. Archaic. a note on a horn, bugle, etc.

…and only when King Alfin was back in Onhava, did he gradually realize from a reiteration of rather frantic questions that he had left somebody behind ("What emperor?" has remained his only memorable mot).
-- Vladimir Nabokov, Pale Fire, 1962

And then as the duchess went on relating a mot with which her mother had snubbed the great Napoleon, it occurred to Newman that her evasion of a chapter of French history more interesting to himself might possibly be a results of an extreme consideration for his feelings.
-- Henry James, The American, 1877

Mot comes from the French word of the same spelling, which in turn is rooted in the Latin word muttum which meant "utterance." It is related to the word motto.