Latin word bellus comes from Proto-Indo-European *deh₂-, and later Proto-Italic *dwenos (Good.)
*deh₂- (Proto-Indo-European)
*dwenos (Proto-Italic)
Good.
dvenos (Latin)
duonus (Old Latin)
optimus (Latin)
Best; very good.
*duenelos (Old Latin)
bellus (Latin)
Beautiful, pretty, handsome. Pleasant, agreeable, charming.