Easton's Bible Dictionary (1897)
Destroyer, the name given to the king of the hosts represented by the locusts (Rev. 9:11). It is the Greek translation of the Hebrew Abaddon (q.v.).
Smith's Bible Dictionary (1863)
or, as it is literally in the margin of the Authorized Version of (Revelation 9:11) “a destroyer,” is the rendering of the Hebrew word Abaddon, “the angel of the bottomless pit.” From the occurrence of the word in (Psalms 88:11) the rabbins have made Abaddon the nethermost of the two regions into which they divide the lower world; but that in (Revelation 9:11) Abaddon is the angel and not the abyss is perfectly evident in the Greek.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
APOL'LYON. See Abaddon.
Hitchcock's Bible Names (1869)
a destroyer