photomotility

The story

1. Proto-Indo-European*bʰeh₂-
2. Proto-Indo-European*bʰéh₂os
3. Proto-Hellenic*pʰáwos
4. Ancient Greekφᾰ́ος (phắos)
5. Ancient Greekφῶς (phôs)
6. Ancient Greekφωτο- (phōto-)
7. Englishphoto-
8. Proto-Indo-European*m(y)ewh₁-
9. Proto-Indo-European*m(y)owh₁éyeti
10. Proto-Italic*moweō
11. Latinmoveō
12. Latinmōtus
13. Englishmotile
14. Englishmotility
15. English todayphotomotility

From photo- + motility.