The etymology of the word is often understood as "lacking worth", from two common words: beli- (בְּלִי "without-") and ya'al ( יָעַל "to be of value").
Image: 'Enter Scorpius' by Al Wiggins Jr.
They had as king over them the angel of the Abyss, whose name in Hebrew is Abaddon and in Greek is Apollyon (that is, Destroyer). Apocalypse 9:11 (NIV) ✝