misdemeanor (n.)

also misdemeanour, late 15c., "ill-behavior, evil conduct, fault," but almost always used in the legal sense of "an indictable offense of less grave nature than a felony;" from mis- (1) "wrong" + Middle English demenure "conduct, management" (see demeanor). Related: Misdemeanors; misdemeanours. Misdemean "behave ill, conduct (oneself) improperly" is from French (and from mis- (2)), but it is attested only from 1560s and is too late to be the source of this word.