nock (n.) Look up nock at
"notch on a bow," late 14c., of uncertain origin, probably from a Scandinavian source (such as Swedish nock "notch"), but compare Low German nokk, Dutch nok "tip of a sail." Perhaps connected to nook.
nock (v.) Look up nock at
"fit (an arrow) to a bowstring," 1510s, from nock (n.). Related: Nocked; nocking.