unartificial

The story

1. Proto-Indo-European*né
2. Proto-Indo-European*n̥-
3. Proto-Germanic*un-
4. Proto-West Germanic*un-
5. Old Englishun-
6. Middle Englishun-
7. Englishun-
8. Proto-Indo-European*h₂er-
9. Proto-Indo-European*h₂értis
10. Proto-Italic*artis
11. Latinars
12. Proto-Indo-European*dʰeh₁-
13. Latinartifex, artificis
14. Latinartificium
15. Proto-Indo-European*h₂el-
16. Proto-Indo-European*h₂élisder.?
17. Latinartificiālis
18. Middle Englishartificial
19. Englishartificial
20. English todayunartificial

From un- + artificial.