undermine

The story

1. Proto-Indo-European*h₁én
2. Proto-Indo-European*h₁entér
3. Proto-Indo-European*h₂én
4. Proto-Indo-European*dʰeh₁-?
5. Proto-Indo-European*(H)n̥dʰí
6. Proto-Indo-European*(H)n̥dʰér
7. Proto-Germanic*under
8. Proto-West Germanic*undar
9. Old Englishunder-
10. Middle Englishunder-
11. Englishunder-
12. Englishmine
13. English todayundermine

From under- + mine.

First known use, by meaning

• from 14th c. To dig underneath (something), to make a passage for destructive or military purposes; to sap.
• from 15th c. To weaken or work against; to hinder, sabotage.