mid-15c., irken "be weary of, be disgusted with;" earlier intransitive, "to feel weary" (early 14c.). Of uncertain origin, perhaps related to Old Norse yrkja "work" (from PIE root *werg- "to work;" see organ), or Middle High German erken "to disgust." Modern sense of "annoy" is from late 15c. An adjective, irk "weary, tired" is attested from c.1300 in northern and midlands writing.