"stiff, coarse hair of certain animals," especially those set along the backs of hogs, Old English byrst "bristle," with metathesis of -r-, from Proto-Germanic *bursti- (source also of Middle Dutch borstel, German borste, Danish börste), from PIE *bhrsti- from root *bhars- "point, bristle" (source also of Sanskrit bhrstih "point, spike"). With -el, diminutive suffix. Extended to similar appendages on some plants and insects.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
<a href="https://www.etymonline.com/word/bristly">Etymology of bristly by etymonline</a>
Harper, D. (n.d.). Etymology of bristly. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/bristly