Do you know ghouls from goblins and ghosts?
c.1200, from a Scandinavian source, cf. Norwegian skulke "to shirk, malinger," Danish skulke "to spare oneself, shirk," Swedish skolka "to shirk, skulk, slink, play truant." Common in Middle English but lacking in 15c.-16c. records; possibly reborrowed 17c. Related: Skulked; skulking; skulker; skulkery.