eleventy

The story

1. Proto-Indo-European*ís?
2. Proto-Indo-European*h₁óynos
3. Proto-Germanic*ainaz
4. Proto-Indo-European*leyp-
5. Proto-Germanic*lībaną
6. Proto-Germanic*ainalif
7. Proto-West Germanic*ainalif
8. Proto-West Germanic*ainalifun
9. Old Englishendleofan
10. Middle Englishelleven
11. Englisheleven
12. Proto-Indo-European*déḱm̥
13. Proto-Indo-European*déḱm̥-t(-s)
14. Proto-Germanic*tegun(dz)
15. Proto-Germanic*teguz
16. Proto-Germanic*tigiwiz
17. Old Englishhundendleftiġ
18. English todayeleventy

From eleven + -ty, from Old English hundendleftiġ (also spelled hundendleofantiġ, hundendlyftiġ, and hundælleftiġ). See twelfty for more. Popularized in the 20th century by J. R. R. Tolkien's The Lord of the Rings trilogy.