legion

Legion entered Middle English (as legioun) around 1200, from Old French legion, from Latin legiō, legionem — itself from legō, meaning "to gather, collect."

It began as the name for a Roman military unit, a body of soldiers literally "collected" together. The looser sense of "a large number" comes from Mark 5:9, where a man possessed by many spirits says, "My name is Legion, for we are many."

It's a distant cousin of legend and lecture, both of which trace back to the same Latin root, legō, "to gather" or "to read." It's also a doublet of León, the Spanish place name.