Suntan

wiktionary

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sun +‎  tan

etymonline

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suntan (v.)

also sun-tan, 1821, from sun (n.) + tan (v.). Related: Suntanned; suntanning. As a noun from 1888. Originally an indication of outdoor laboring; considered as an enhancement to beauty or proof of idleness from 1920s: F.L. Allen, chronicler of the decade ("Only Yesterday"), notes 1929 as the year that "on the sands of a thousand American beaches, girls pulled down the shoulder-straps of their bathing suits to acquire fashionably tanned backs ...."