laugh-out-loud

The story

1. Proto-Indo-European*klek-
2. Proto-Germanic*hlahjaną
3. Proto-West Germanic*hlahhjan
4. Old Englishhliehhan
5. Old Englishhlæhhan
6. Middle Englishlaughen, laghen
7. Englishlaugh
8. Proto-Indo-European*úd
9. Proto-Germanic*ūt
10. Proto-West Germanic*ūt
11. Old Englishūt
12. Proto-Germanic*ūt
13. Proto-Germanic*ūtai
14. Proto-West Germanic*ūtē
15. Old Englishūte
16. Middle Englishoute
17. Englishout
18. Proto-Indo-European*ḱel-
19. Proto-Indo-European*ḱlew-
20. Proto-Indo-European*ḱlutós
21. Proto-Germanic*hlūdaz
22. Proto-Germanic*hlūdê
23. Proto-West Germanic*hlūdē
24. Old Englishhlūde
25. Middle Englishloude
26. Englishloud
27. English todaylaugh-out-loud

From laugh + out + loud.