R. Eliezer says: (the verse is) acronymic: "vayachalosh" — "and he broke"; "Amalek" — as stated; "eth Amalek" — his wife and children; "amo" — the warriors "imo" ("with him"); "eth amo" — the warriors with his children.
Rabbi Eliezer Decodes the Hidden Acronym in Joshua's Victory
Mekhilta Tractate Amalek 1:37