Here's my take on a direct translation of the Heavensward lyrics;
Dis | an | sô
Disturbed | our | slumber
Rus | at | hi
Brother | mine | wake
Sal'jas | afarr'a
Will be | vengeance ours
Ma | mor | nâ | Eorzea!
Must | perish | the | Saviors!
With that, it would seem "an" is, in fact, Our or Ours, depending on context, "Afah" - Vengeance, and "Morn" - Perish.
So, if I'm correct, which I think I am, we'd be looking at "Akh Vengeance Amphitheatre" and "Akh Perish".
It'd be nice to see "Akh" in context somewhere...
I'm no linguist btw, this is just 5 minutes of me trying to match words.
EDIT: Looking at these lyrics again, and sorry if it's a bit off topic, I can't help but be reminded of Nidhogg. The title "Of the Vengeful Lance" comes to mind and pairs well with "Slumber disturbed" if you think about it....