Meaning

noun a joint of a finger when the fist is closed

verb press or rub with the knuckles

verb shoot a marble while keeping one's knuckles on the ground

originFrom Middle English knokel (“finger joint”), from Old English cnucel (“the juncture of two bones; knuckle; joint”), from Proto-West Germanic *knukil, from Proto-Germanic *knukilaz (“knuckle, knot, bump”), as *knukô (“bone, joint”) + *-ilaz (diminutive suffix). Cognate with Dutch knokkel (“knuckle”), Low German Knökel (“knuckle”), German Knöchel (“ankle, knuckle”), Old Norse knykill. More at knock.

Etymology from Wiktionary, CC BY-SA 3.0