nonterminal

The story

1. Proto-Indo-European*né
2. Proto-Germanic*ne
3. Proto-Indo-European*ís?
4. Proto-Indo-European*h₁óynos
5. Proto-Germanic*ainaz
6. Proto-Germanic*nainaz
7. Proto-West Germanic*nain
8. Old Englishnān
9. Middle Englishnon
10. Old Englishnān
11. Old Englishnān-
12. Middle Englishnon-
13. Englishnon-
14. Proto-Indo-European*terh₂-?
15. Proto-Indo-European*ter-?
16. Proto-Indo-European*térmn̥
17. Proto-Italic*termn̥
18. Proto-Italic*term(e)nos
19. Latinterminus
20. Proto-Indo-European*h₂el-
21. Proto-Indo-European*h₂élisder.?
22. Late Latinterminālis
23. Englishterminal
24. English todaynonterminal

From non- + terminal.