Hebrew name (אֲבַדּוֹן) - "death; extermination". The Greek equivalent of the name Apollo.
In the Old Testament, Abaddon refers to one of the regions of hell (Gehenna). Abbadon is the Abyssal Angel, a powerful demon of death and of destruction, the military adviser of Hell. Abbadon is repeatedly mentioned in the Bible along with hell and death and was repeatedly used in the Middle Ages as one of the designations of Satan, although some sources hi still refer to holy angels, obedient to God's will.