Wistful

Origin

Presumably from *whistful, from whist ("silent") + -ful, based on older wistly. It is implausible that it derives from wishful, the required sound change being wishful → *wisful → wistful, and could not occur in Modern English, particularly not with wishful continuing in use. However, the sense of “longing” appears to be influenced by wishful, with wistful being an ambiguous poetic word.

Century Dictionary, wistful etymology at WordNik

Full definition of wistful

Adjective

1. full of yearning or longingHis eyes grew wistful as he recalled his university days.
2. sad and thoughtful

Synonyms

• (thoughtful sadness) melancholy