subnormal

The story

1. Proto-Indo-European*upó
2. Proto-Italic*supo
3. Latinsub
4. Latinsub-
5. Englishsub-
6. Proto-Indo-European*ǵneh₃-
7. Proto-Indo-European*ǵn̥h₃sḱéti
8. Proto-Hellenic*gignṓskō
9. Ancient Greekγιγνώσκω (gignṓskō)
10. Ancient Greekγνώμων (gnṓmōn)
11. Latinnorma
12. Proto-Indo-European*h₂el-
13. Proto-Indo-European*h₂élisder.?
14. Latinnōrmālis
15. Englishnormal
16. English todaysubnormal

From sub- + normal.