Adding to this, in the trailer, Wallace says something along the lines of "I never knew we received it from that huge man in the Kalos region..." likely referring to Mega Evolution.This one's easy.
Zinnia is a flower
Higana comes from "higanbana" which means "spider lily" (oh hey another flower)
In the language of flowers, Zinnias equate to the remembrance of those dearly departed. Red Spider Lillies are often called "the flower that blooms in the afterlife" because they're commonly found growing around cemeteries. In Japanese culture/art, they are used to depict a sorrowful scene of two people who will never meet again, likely because one of them is about to get killed off.
So Zinnia has a very strong life/death/afterlife and "unto ancient magic" theme spelled out for her. What were the species names for Xerneas and Yveltal ?
~XY remake confirmed~
Also, Wallace knows about Az. Huh.