Where does “Γεννάριος” come from?

Γεννάριος (Byzantine Greek) comes from Latin ianuarius, from Latin Ianus, from Latin ianus, from Proto-Indo-European yeh₂- — to go; to go in, enter; to ride, to travel.

Ancestry of “Γεννάριος”, step by step

Step	Language	Word	Meaning
1	Latin	ianuarius	Of January; January, short for mēnsis iānuārius
2	Latin	Ianus	the Roman god Janus; Roman god of doorways;...
3	Latin	ianus	arcade; covered passageway
4	Proto-Indo-European	yeh₂-	to go; to go in, enter; to ride, to travel

Every word from Proto-Indo-European yeh₂- →Every word from Latin ianus →Every word from Latin Ianus →