Tan
late Old English tannian ‘convert into leather’, probably from medieval Latin tannare, perhaps of Celtic origin; reinforced in Middle English by Old French tanner . Early use of the noun (late Middle English) was in tan1 (sense 3 of the noun).
wiktionary
Borrowed from French tan(“tanbark”), from Gaulish tanno-(“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(“woods”), Tanne(“fir”), Albanian thanë(“cranberry bush”), Ancient Greek θάμνος(thámnos, “thicket”), Avestan 𐬚𐬀𐬥𐬎𐬎𐬀𐬭𐬆 (θanuuarə), Sanskrit धनु(dhánu).
As a verb, from Middle English tannen, from late Old English tannian(“to tan a hide”), from Latin tannare.
From a Brythonic language; influenced in form by yan(“one”) in the same series.
Borrowed from Armenian թան(tʿan).
From the Cantonese pronunciation of 擔
From Old English tān(“twig, switch”), from Proto-Germanic *tainaz(“rod, twig, straw, lot”).
etymonline
tan (v.)
late Old English tannian "to convert hide into leather" (by steeping it in tannin), from Medieval Latin tannare "tan, dye a tawny color" (c. 900), from tannum "crushed oak bark," used in tanning leather, probably from a Celtic source (such as Breton tann "oak tree"). The meaning "make brown by exposure to the sun" (as tanning does to hides) first recorded 1520s; intransitive sense also from 1520s. Of persons, not considered an attractive feature until 20c.; in Shakespeare, "to deprive of the freshness and beauty of youth" (Sonnet CXV). As an adjective from 1620s. To tan (someone's) hide in the figurative sense is from 1660s. Related: Tanned; tanning. German Tanne "fir tree" (as in Tannenbaum) might be a transferred meaning from the same Celtic source.
tan (n.)
"bronze color imparted to skin by exposure to sun," 1749, see tan (v.). Earlier as "substance made of crushed bark used in making leather" (c. 1600). As a simple name for a brownish color, in any context, it is recorded from 1888. The adjective meaning "of the color of tanned leather" is recorded from 1660s. Tan-line attested from 1979.
