Merriam-Webster's Collegiate® Dictionary, 11th Edition
TAN
I. verb (tanned; tanning)
Etymology: Middle English tannen, from Anglo-French tanner, from Medieval Latin tannare, from tanum, tannum tanbark
Date: 13th century
transitive verb
1. to convert (hide) into leather by treatment with an infusion of tannin-rich bark or other agent of similar effect, to convert (protein) to leather or a similar substance, to make (skin) tan especially by exposure to the sun, thrash , whip , intransitive verb to get or become tanned,
II. adjective (tanner; tannest)
Date: 1586
of, relating to, or used for tan or tanning, of the color tan,
III. noun
Etymology: French, tanbark, from Old French, from Medieval Latin tanum
Date: 1674
a tanning material or its active agent (as tannin), a brown color imparted to the skin especially by exposure to the sun, a light yellowish brown, tan-colored articles of clothing,
IV. abbreviation tangent