* Participle/Adjective: From the perfect passive participle of videō (“I see”). (Diachronically, from Proto-Italic *wissos, from Proto-Indo-European *widtós.)
* Fourth-declension noun: From Proto-Italic *weissus or *wissus, from Proto-Indo-European *wéydˢtus. Cognate with Old Irish fius (“knowledge”).
Both ultimately from the root *weyd- (“to see, know”).