@ Hunlight
thedemonsmaster below probably is right, in the "Abaddon" name (better known as Apollyon).
Likewise, the "sĂdhe" (p.8) probably borrows from the people of the mounds https://en.wikipedia.org/wiki/Aos_SĂ
(for instance, one could know 'the mounds' from the popular banshee - ben sĂdhe)
In any case, that's your choice as translators, so no complaints here. Good job and thanks!