Do you know ghouls from goblins and ghosts?
late 15c., gagyll, with reference to both geese and women. Barnhart says possibly from Old Norse gagl "small goose, gosling, bird;" OED calls it "one of the many artificial terms invented in the 15th c. as distinctive collectives referring to particular animals or classes of persons." Possibly of imitative origin (cf. Dutch gagelen "to chatter;" Middle English gaggle "to cackle," used of geese, attested from late 14c.).