Other forms: knuckles
A knuckle is one of the bumps where a finger bends. Crack your knuckles, bruised knuckles, rap on the door with a knuckle.
Cracking them is the gas bubbles in the joint fluid collapsing, and the long-standing claim that it causes arthritis has been tested and found false. Knuckle down means to get to work, and knuckle under means to submit.
1nounknuckleOne of the bumps where a finger bends.
“He knocked on the door so hard that his knuckles hurt.”
knuckle is a joint.
Middle English knokel comes from a Germanic root meaning a joint or bone-end. Knee and knob are distant relatives.
Proto-Germanic
*knukilaz — knuckle, knot, bump
Proto-West Germanic
*knukil
Old English
cnucel — the juncture of two bones; knuckle; joint
Middle English
knokel — finger joint
English, today
knuckle
From 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 + -ilaz. 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