nook (n.)

"a notch," specifically, in archery, "the notch on the horn of a bow," where the string is fastened, also "notch on the end of an arrow," which rests on the string, late 14c., nokke, a word of uncertain origin, probably from a Scandinavian source (such as Swedish nock "notch"), or a continental Germanic one such as Low German nokk, Middle Dutch nocke, Dutch nok "tip of a sail" or other similar words denoting projections or tips. Perhaps connected to nook.

also nooky, "sexual activity," slang, generally used by men, by 1928, perhaps from Dutch neuken "to copulate with," but it is not impossible to connect it to nook (n.) on the notion of "an angle" or "a secluded spot." The adjective nooky "full of nooks, nook-like" is recorded from 1813.