The story
- Proto-Indo-European*upó
- Proto-Italic*supo
- Latinsub
- Latinsub-
- Englishsub-
- Proto-Indo-European*gʷʰiH-(s-)lo-
- Proto-Italic*fī(s)lom
- Latinfīlum
- Late Latinfīlō
- Medieval Latinfīlāmentum
- Englishfilament
- Proto-Indo-European*h₂el-
- Proto-Indo-European*h₂élisder.?
- Englishfilamental
- English todaysubfilamental
From sub- + filamental.
Etymology from Wiktionary, CC BY-SA 4.0.