anaerobically

The story

1. Proto-Indo-European*né
2. Proto-Indo-European*n̥-
3. Proto-Hellenic*ə-
4. Ancient Greekᾰ̓- (ă-)
5. Ancient Greekἀν- (an-)
6. Proto-Indo-European*h₂ews-
7. Proto-Indo-European*h₂ewsér
8. Proto-Hellenic*auhḗr
9. Ancient Greekᾱ̓ήρ (āḗr)
10. Proto-Indo-European*gʷeyh₃-
11. Ancient Greekβῐ́ος (bĭ́os)
12. Frenchanaérobie
13. Englishanaerobic
14. Proto-Indo-European*h₂el-
15. Proto-Indo-European*h₂élisder.?
16. Proto-Indo-European*leyg-
17. Proto-Germanic*līką
18. English todayanaerobically

From anaerobic + -ally.