Where does “hexagramme” come from?

hexagramme (English) comes from English gramme — gram.

Ancestry of “hexagramme”, step by step

hexagramme traces back through two separate lines of ancestry.

via English gramme

StepLanguageWordMeaning
1Englishgrammegram

via English hexa

StepLanguageWordMeaning
1Englishhexa
Every word from English gramme