longterm

The story

1. Proto-Indo-European*dlongʰos
2. Proto-Germanic*langaz
3. Proto-West Germanic*lang
4. Old Englishlang
5. Middle Englishlong
6. Englishlong
7. Proto-Indo-European*terh₂-?
8. Proto-Indo-European*ter-?
9. Proto-Indo-European*térmn̥
10. Proto-Italic*termn̥
11. Proto-Italic*term(e)nos
12. Latinterminus
13. Old Frenchterme
14. Middle Englishterme
15. Englishterm
16. English todaylongterm

From long + term.