of horses, cows, dogs, etc., "marked with streaks, streaked with a darker color," 1670s, variant of Middle English brended (early 15c.), from bren "brown color" (13c.), noun from past participle of brennen "burn" (from Proto-Germanic *brennan "to burn," from PIE root *gwher- "to heat, warm"). The etymological sense of the adjective appears to be "marked as though by branding or burning." Form altered perhaps by influence of kindled.
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<a href="https://www.etymonline.com/word/brindle">Etymology of brindle by etymonline</a>
Harper, D. (n.d.). Etymology of brindle. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/brindle