O.E. hacele "cloak, mantle" (cf. O.H.G. hachul, Goth. hakuls "cloak;" O.N. hekla "hooded frock"). Sense of "bird plumage" is first recorded 1496, though this may be from unrelated M.E. hackle "flax comb" (see
heckle) on supposed resemblance of comb to ruffled feathers. Metaphoric