c. 1400, from Latin Myrmidones (plural), from Greek Myrmidones, Thessalian tribe led by Achilles to the Trojan War, fabled to have been ants changed into men, and often derived from Greek myrmex "ant" (from PIE *morwi- (see Formica (2)), but Watkins does not connect them and Klein's sources suggest a connection to Greek mormos "dread, terror." Transferred sense of "faithful follower" is from c. 1600.