Meaning

noun archaic terms for army

noun association of ex-servicemen

noun a large military unit

originAttested (in Middle English, as legioun) around 1200, from Old French legion, from Latin legiō, legionem, from legō (“to gather, collect”); akin to legend, lecture. Doublet of León, which was borrowed from Spanish. Generalized sense of “a large number” is due to an allusive phrase in Mark 5:9, "My name is Legion, for we are many".

Etymology from Wiktionary, CC BY-SA 3.0