The story
- Proto-Germanic*handuz
- Proto-West Germanic*handu
- Old Englishhand
- Middle Englishhond
- Proto-Indo-European*sem-
- Proto-Indo-European*somHós
- Proto-Germanic*samaz
- Middle Englishhondsom
- English todayhandsome
From Middle English handsum, hondsom, equivalent to hand + -some. Compare Dutch handzaam, German Low German handsaam. The original sense was “easy to handle or use”, hence “suitable” and “apt, clever” (mid-16th century), giving rise to the current appreciatory senses (late 16th century).
Etymology from Wiktionary, CC BY-SA 4.0.