c.1500, from Middle English ampte (late 14c.), from Old English æmette "ant," from West Germanic *amaitjo (cf. Old High German ameiza, German Ameise) from a compound of bases *ai- "off, away" + *mai- "cut," from PIE *mai- "to cut" (cf. maim). Thus the insect's name is, etymologically, "the biter off."
As þycke as ameten crepeþ in an amete hulle [chronicle of Robert of Gloucester, 1297]Emmet survived into 20c. as an alternative form. White ant "termite" is from 1729. To have ants in one's pants "be nervous and fidgety" is from 1934, made current by a popular song; antsy embodies the same notion.
To be nervous or anxious; to be fidgety: he has ants in his pants waiting for the audition