nonimpressed

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*h₁én
15. Proto-Italic*en
16. Proto-Italic*en-
17. Latinin-
18. Proto-Indo-European*per-?
19. Proto-Indo-European*pres-
20. Proto-Italic*pres-
21. Latinpremō
22. Latinimprimō
23. Latinimpressus
24. Middle Englishimpressen
25. Englishimpressed
26. English todaynonimpressed

From non- + impressed.