idiomotor

The story

1. Proto-Indo-European*swé
2. Proto-Indo-European*swéd-yo-s
3. Proto-Hellenic*hwédios
4. Ancient Greekῐ̓́δῐος (ĭ́dĭos)
5. Englishidio-
6. Proto-Indo-European*m(y)ewh₁-
7. Proto-Indo-European*m(y)owh₁éyeti
8. Proto-Italic*moweō
9. Latinmoveō
10. Latinmōtor
11. Middle Englishmotour
12. Englishmotor
13. English todayidiomotor

From idio- + motor.