diphosphate

The story

1. Proto-Indo-European*dwóh₁
2. Proto-Indo-European*dwi-
3. Proto-Hellenic*dwi-
4. Ancient Greekδῐ- (dĭ-)
5. Latindi-
6. Englishdi-
7. Proto-Indo-European*bʰeh₂-
8. Proto-Indo-European*bʰéh₂os
9. Proto-Hellenic*pʰáwos
10. Ancient Greekφᾰ́ος (phắos)
11. Ancient Greekφῶς (phôs)
12. Proto-Indo-European*bʰer-
13. Proto-Indo-European*bʰéreti
14. Proto-Hellenic*pʰérō
15. Ancient Greekφέρω (phérō)
16. Ancient Greekφωσφόρος (phōsphóros)
17. Latinphōsphorus
18. Frenchphosphore
19. Frenchphosphate
20. Englishphosphate
21. English todaydiphosphate

From di- + phosphate.