Old English hacele "coat, cloak, vestment, mantle" (cognate with Old High German hachul, Gothic hakuls "cloak;" Old Norse hekla "hooded frock"), of uncertain origin. The same word with a sense of "bird plumage" is first recorded early 15c., though this might be from unrelated Middle English hackle "flax comb" (see heckle (n.)) on supposed resemblance of comb to ruffled feathers, or from an unrecorded continental Germanic word. Metaphoric extension found in phrases such as raise (one's) hackles (as a cock does when angry) is by 1881.[hackle etymology, hackle origin, 英语词源]