| Definition -
Words that are either:
(1) spelled the same but have different meanings (e.g. bank as in money in the bank and bank of the river);
(2) sound alike but aren't spelled the same (e.g. coarse and course); and
(3) spelt the same but do not sound the same (e.g. lead a horse to water and brains made of lead).
Etymology - The word derives via Latin from the Greek homonymos, same name (from homos, same + onyma, name).
Oxford English Dictionary - Its first citation is from 1697:
"Those [words] that differ not in termination; as grammatica, the art of grammar, and grammatica, a woman, are not conjugates, but homonyms."
(tr. Burgersdicius his Logic i. xxv. 100)