"instrument consisting of flexible material (bristles, hair, etc.) attached to a handle or stock," late 14c., "dust-sweeper, a brush for sweeping," from Old French broisse, broce "a brush" (13c., Modern French brosse), perhaps from Vulgar Latin *bruscia "a bunch of new shoots" (used to sweep away dust), perhaps from Proto-Germanic *bruskaz "underbrush." Compare brush (n.2). As an instrument for applying paint, late 15c.; as an instrument for playing drums, 1927. Meaning "an application of a brush" is from 1822.
"shrubbery, small trees and shrubs of a wood; branches of trees lopped off," mid-14c., from Anglo-French bruce "brushwood," Old North French broche, Old French broce "bush, thicket, undergrowth" (12c., Modern French brosse), from Gallo-Roman *brocia, perhaps from *brucus "heather," or possibly from the same source as brush (n.1).
late 15c., "clean or rub (clothing) with a brush," also (mid-15c.) "beat with a brush," from brush (n.1). The meaning "move or skim over with a slight contact" is from 1640s. Related: Brushed; brushing. To brush off someone or something, "rebuff, dismiss," is from 1941. To brush up is from c. 1600 as "clean by brushing;" the figurative sense of "revive or refresh one's knowledge" of anything is from 1788.
"move briskly" especially past or against something or someone, 1670s, from earlier sense "to hasten, rush" (c. 1400); probably from brush (n.2) on the notion of a horse, etc., passing through dense undergrowth (compare Old French brosser "to dash (through woods or thickets)," and Middle English noun brush "charge, onslaught, encounter," mid-14c.). But brush (n.1) probably has contributed something to it, and OED suggests the English word could be all or partly onomatopoeic. Related: Brushed; brushing.