Where does “six” come from?

six (Old French) comes from Latin sex, from Proto-Italic seks, from Proto-Indo-European swéḱs — six.

Ancestry of “six”, step by step

StepLanguageWordMeaning
1Latinsexsix; 6
2Proto-Italicsekssix
3Proto-Indo-Europeanswéḱssix
Every word from Proto-Indo-European swéḱs →Every word from Proto-Italic seks →Every word from Latin sex →