Meaning

noun a browning of the skin resulting from exposure to the rays of the sun

noun a light brown the color of topaz

noun ratio of the opposite to the adjacent side of a right-angled triangle

originFrom Middle English tan, from Old French tan (“tanbark”), from Gaulish *tannos (“green oak”) – compare Breton tann (“red oak”), Old Cornish tannen –, from Proto-Celtic *tannos (“green oak”), of uncertain origin, but perhaps from Proto-Indo-European *(s)dʰonu (“fir”). Per this hypothesis, related to Hittite [script needed] (tanau, “fir”), Latin femur, genitive feminis (“thigh”), German Tann…

Etymology from Wiktionary, CC BY-SA 3.0