face-busting, hand-protecting metal knuckle-guard, 1857, from knuckle (n.) + duster, name of a type of protective coat worn by workmen.
Entries linking to knuckle-duster
knuckle n.
mid-14c., knokel "finger joint; any joint of the body, especially a knobby one; morbid lump or swelling." Perhaps in Old English, but not attested there. Common Germanic (compare Middle Low German knökel, Middle Dutch cnockel, German knöchel), literally "little bone," a diminutive of Proto-Germanic root *knuk- "bone," which is not represented in English in its simple form (but compare German Knochen "bone). For pronunciation, see kn-.
duster n.
1570s, "dust brush for clothes," agent noun from dust (v.). Meaning "sifter, fine sieve" is from 1660s; that of "light overcoat or wrap worn to keep off dust from clothing" is from 1864.