verb (used with object), knuck·led, knuck·ling.
- to apply oneself vigorously and earnestly; become serious: Just knuckle down for an hour or so and finish the work.
- Also knuckle under.to submit; yield.
Origin of knuckle
Word Origin for knuckle
mid-14c., knokel "finger joint; any joint of the body, especially a knobby one; morbid lump or swelling;" common Germanic (cf. Middle Low German knökel, Middle Dutch cnockel, German knöchel), literally "little bone," a diminutive of Proto-Germanic root *knuck- "bone" (cf. German Knochen "bone).
As a verb from 1740, originally in the game of marbles. To knuckle down "apply oneself earnestly" is 1864 in American English, extended from marbles (putting a knuckle on the ground in assuming the hand position preliminary to shooting); to knuckle under "submit, give in" is first recorded 1740, supposedly from the former more general sense of "knuckle" and here meaning "knee," hence "to kneel." The face-busting knuckle-duster is from 1858 (a duster was a type of protective coat worn by workmen).
Apply oneself seriously to some task or goal, as in The professor insisted that we knuckle down and get our papers in by Friday. Both this term and the rhyming synonym buckle down date from the 1860s, but the precise allusion in either is unclear.
See knuckle under.
In addition to the idioms beginning with knuckle
- knuckle down
- knuckle under
- rap someone's knuckles