nonanswer

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*h₂ent-
15. Proto-Indo-European*h₂énts
16. Proto-Germanic*anda-
17. Proto-Indo-European*swer-
18. Proto-Germanic*swarō
19. Proto-Germanic*andaswarō
20. Proto-West Germanic*andaswaru
21. Old Englishandswaru
22. Middle Englishanswere
23. Englishanswer
24. English todaynonanswer

From non- + answer.