Aelvinnwode is not Anuirean or Old Andu, it is Rjurik as printed in the initial materials.

The Rjurik settled the northernmost regions (Hjalsone) of the forest before the tribes of the Andu did.

Page 19 of the Atlas states:

"In the old tongue of the Rjurik, Aelvinnwode simply means "elven wood." Once..."

The later invasions and conquest of all the Aelvinnwode by Anuireans doesn't mean that this word is Anuirean.