The word 'wan' originates from the Old English wann, which carried the sense of "dark, dusky, gloomy." This meaning likely evolved from a Proto-Germanic root concerned with the absence or deficiency of light. Over centuries, the semantic focus shifted from describing the darkness of an environment to describing a human complexion that is unnaturally pale, ashen, or lacking healthy color, as if drained of light and vitality. Consequently, the modern abstract meaning retains this core idea of deficiency, now applied specifically to a sickly pallor or a feeble quality of light.

This word is a simplex. It is a loanword from Old English wann meaning "dark, dusky, lacking light." Its functional role is as a complete adjective root.