Meaning

noun the sound of knocking (as on a door or in an engine or bearing)

noun negative criticism

noun a vigorous blow

originFrom Middle English knokken, from Old English cnocian, ġecnocian, ġecnucian, cnucian (“to knock, pound on, beat”), from Proto-West Germanic *knokōn, from Proto-Germanic *knukōną (“to knock”), a suffixed form of *knu-, *knew- (“to pound on, beat”), from Proto-Indo-European *gnew-, *gen- (“to squeeze, pinch, kink, ball up, concentrate”). The English word is cognate with Middle High German knochen…

Etymology from Wiktionary, CC BY-SA 3.0