Wan

wan \ˈwän\ adjective: 1 a. suggestive of poor health; sickly, pallid, b. lacking vitality; feeble, 2: dim, faint, 3: languid {a wan smile}

Etymology: Middle English, from Old English wann dark, livid

We all know this word from Sir John Suckling’s “Why So Pale and Wan, Fond Lover?”