magnetoacoustic

The story

1. Ancient GreekΜάγνης (Mágnēs)
2. Ancient Greekμᾰ́γνης (mắgnēs)
3. Old Frenchmagnete
4. Ancient Greekμᾰ́γνης (mắgnēs)
5. Latinmagnēs
6. Middle Englishmagnete
7. Englishmagnet
8. Englishmagnet-
9. Englishmagneto-
10. Proto-Indo-European*h₂eḱ-
11. Proto-Indo-European*h₂ew-
12. Proto-Indo-European*h₂ṓws
13. Proto-Indo-European*h₂ḱh₂owsyéti
14. Proto-Hellenic*akóuhō
15. Ancient Greekἀκούω (akoúō)
16. Ancient Greekᾰ̓κουστῐκός (ăkoustĭkós)
17. Medieval Latinacousticus
18. Englishacoustic
19. English todaymagnetoacoustic

From magneto- + acoustic.