Do you know ghouls from goblins and ghosts?
late 14c., a native coinage or else from Flemish gulpe or Dutch gulpen "to gush, pour forth, guzzle, swallow," in any case possibly of imitative origin (cf. Swedish dialectal glapa "to gulp down"). Related: Gulped; gulping.
1560s, from gulp (v.), or else from Flemish gulpe, Dutch gulp "stream of water, large draught."