Mim

Prudish, prim , and discreetly silent, applied only to women; of contemptuously to effeminate men, as in the phrase, " He's as mim as a maiden." In this sense the word is distinguished from mum, which means silent, or secret only, without reference to sex, as in the current slang, "mum's the word" ... The word mim has a meaning of its own, which should preserve it in the language. It is derived by some authorities from the Greek mimeo, to imitate by action without speaking; whence mimicry, mimic, and pantomime.

- Charles Mackay's Lost Beauties of the English Language, 1874.