"of ill repute," late 14c., from Medieval Latin infamosus, from Latin in- "not, opposite of" (see in-(1)) + famosus "celebrated" (see famous). Meaning influenced by Latin infamis "of ill fame" (see infamy). As a legal term, "disqualified from certain rights of citizens in consequence of conviction of certain crimes" (late 14c.). The neutral fameless is recorded from 1590s. Related: Infamously.