Strong’s Greek
G623 — Apolluon
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
Ἀπολλύων
Apolluon — pronounced ap-ol-loo'-ohn
active participle of 622; a destroyer (i.e. Satan):--Apollyon. see GREEK for 622
1 occurrence in the KJV.
Revelation 9:11
And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.