the word 'suntan' is a transparent modern english compound, formed from two ancient germanic roots. 'sun' derives from proto-germanic sunnōn, ultimately from the proto-indo-European root sóh₂wl̥, meaning 'the sun'. 'tan' originates from old english tannian, meaning to convert hide into leather using tannin, a process that turns the material brown. by the early 20th century, as leisure exposure to the sun became culturally popular, the verb 'tan' was semantically extended to describe the skin's browning reaction to sunlight, leading to the straightforward compound 'suntan' to specify this particular cause and effect.

Structure: sun (star) + tan (brown colour) sun (old english, functional role: noun, the source of light and heat); tan (old english, functional role: noun/verb, to convert hide into leather, later extended to the brown colour produced)