Abaddon is a Hebrew word meaning destruction.
In poetry it comes to mean place of destruction, and so the underworld or Sheol (cf. Job xxvi. 6; Prov. xv. 11). In Rev. ix. 11 Abaddon ((Abaddon) is used of hell personified, the prince of the underworld. The term is here explained as Apollyon (q.v.), the destroyer. , W. Baudissin (Herzog-Hauck, Realencyklo padie) notes that Hades and Abaddon in Rabbinic writings are employed as personal names, just as shemayya in Dan. iv. 23, shamayim (heaven), and makom (place) among the Rabbins, are used of God.
From Gutenberg Encyclopedia (1911)
In demonology he is considered the master of certain goblins and, according to Francis Barrett, the prince of wars and evilness against goodness.
See also Barrett's classification of demons.