The story
- Proto-Indo-European*swéḱs
- Proto-Hellenic*hwéks
- Ancient Greekἕξ (héx)
- Ancient Greekἑξα- (hexa-)
- Latinhexa-
- Englishhexa-
- Proto-Indo-European*déḱm̥
- Proto-Hellenic*dékə
- Ancient Greekδέκᾰ (dékă)
- Ancient Greekδεκάς (dekás)
- Late Latindecas
- Frenchdéca-
- Englishdeca-
- English todayhexadeca-
From hexa- (“six”) + deca- (“ten”). Compare Ancient Greek ἑκκαίδεκα (hekkaídeka, “sixteen”).
Etymology from Wiktionary, CC BY-SA 4.0.