bristle (n.) Look up bristle at Dictionary.com
Old English byrst "bristle," with metathesis of -r-, from Proto-Germanic *bursti- (cognates: Middle Dutch borstel, German borste), from PIE *bhrsti- from root *bhars- "point, bristle" (cognates: Sanskrit bhrstih "point, spike"). With -el, diminutive suffix.
bristle (v.) Look up bristle at Dictionary.com
c.1200 (implied in past participle adjective bristled) "set or covered with bristles," from bristle (n.). Meaning "become angry or excited" is 1540s, from the way animals show fight. Related: Bristling.