auburn (adj.)

early 15c., "whitish, yellowish-white, flaxen-colored," from Old French auborne, from Medieval Latin alburnus "off-white, whitish," from Latin albus "white" (see alb). Meaning shifted 16c. to "reddish-brown" under influence of Middle English brun "brown" (see brown (adj.)) which also changed the spelling. Since the sense-shift it has generally been limited to hair. As a noun by 1852.