What does archi- mean?
The definition of archi-
Ar”chi-.
Etym: [L., archi-, Gr. arce-, erce-, OHG. erzi-.]

A prefix signifying chief, arch; as, architect, archiepiscopal. In Biol. and Anat. it usually means primitive, original, ancestral; as, archipterygium, the primitive fin or wing.