well Angel is Angel and lore is wisdom so it probably means the wisdom of an angel or something like that... :unsure:
Well even the group name Tristania is based on a real word "Tris" but then adecuated in a poetic form.
"Angellore revered at dusk
For thee I rose, now descend all alone
Rise for me, soothe my heart
So wide a sea, may I overcome"
It is the only part of the song where the word Angellore is used. I think Angelore is just a poetical word which rhymes with ROSE. Of course they could have besed themselves on angel and Lore.
But Angellore is reffered to an angel but not to a common angel:
"Into the night strays an angel
So lost and tearful all astray[...]"