means A minor criminal offense that's punishable but less serious than a felony — think petty theft or disorderly conduct, not grand schemes.

from A tidy assembly job: the prefix 'mis-' (meaning 'wrongly' or 'badly,' a Germanic inheritance) bolted onto 'demeanor,' which comes from the verb 'demean' in its older, neutral sense of 'to conduct oneself' — from Old French 'demener,' 'to lead' or 'manage' (de- plus 'mener,' to lead, from Latin 'minare,' to drive cattle). So a misdemeanor is literally a mis-behaving, a conducting-of-oneself gone wrong. The word surfaced in English legal language in the 15th century. The unrelated, sneering sense of 'demean' — to lower or degrade — came later and by a separate path.