Where does “6ter” come from?

6ter (French) comes from French six, from Middle French six, from Old French sis, from Latin sex, from Proto-Italic seks, from Proto-Indo-European swéḱs — six.

6ter (French): 6ter

Definitions

6ter

Ancestry of “6ter”, step by step

6ter traces back through two separate lines of ancestry.

via French six

Step	Language	Word	Meaning
1	French	six	six
2	Middle French	six	six
3	Old French	sis	six
4	Latin	sex	six; 6
5	Proto-Italic	seks	six
6	Proto-Indo-European	swéḱs	six

via English sister

Step	Language	Word	Meaning
1	English	sister	A daughter of the same parents as another person;...
2	Middle English	suster	A sister or step-sister; a female sibling
3	Old English	sweostor	sister
4	Proto-West Germanic	*swester	sister

Every word from Proto-Indo-European swéḱs →Every word from Proto-Italic seks →Every word from Latin sex →