Most believe the abyss to be speaking of the empty earth.
The word abusos is the same in the LXX (Greek OT) as here, as noted above.
However, given other texts in Revelation that speak of the abyss, and at least one text in Luke, this becomes a problematic interpretation.
The bottomeless pit here is the same word, and is the rendering given in the KJV on the passage in question.
Rev 9:1 And the fifth angel sounded, and I saw a star fall from heaven unto the earth: and to him was given the key of the bottomless pit.
Rev 9:2 And he opened the bottomless pit; and there arose a smoke out of the pit, as the smoke of a great furnace; and the sun and the air were darkened by reason of the smoke of the pit.
Rev 9:3 And there came out of the smoke locusts upon the earth: and unto them was given power, as the scorpions of the earth have power.
Rev 9:4 And it was commanded them that they should not hurt the grass of the earth, neither any green thing, neither any tree; but only those men which have not the seal of God in their foreheads.
Rev 9:5 And to them it was given that they should not kill them, but that they should be tormented five months: and their torment was as the torment of a scorpion, when he striketh a man.
Rev 9:6 And in those days shall men seek death, and shall not find it; and shall desire to die, and death shall flee from them.
Rev 9:7 And the shapes of the locusts were like unto horses prepared unto battle; and on their heads were as it were crowns like gold, and their faces were as the faces of men.
Rev 9:8 And they had hair as the hair of women, and their teeth were as the teeth of lions.
Rev 9:9 And they had breastplates, as it were breastplates of iron; and the sound of their wings was as the sound of chariots of many horses running to battle.
Rev 9:10 And they had tails like unto scorpions, and there were stings in their tails: and their power was to hurt men five months.
Rev 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.
Rev 11:7 And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.
Luk 8:30 Jesus then asked him, "What is your name?" And he said, "Legion," for many demons had entered him.
Luk 8:31 And they begged him not to command them to depart into the abyss.
The above texts give an indication that there was an abyss before the empty earth where spirits were held or restrained in some way. The locusts came out of the pit during the trumpets, while the inhabitants of the earth were still around. In chapter 17 we see reference to the one who will come out of the abyss, to go to destruction...that would be Satan who is bound there later. The point being, the abyss was around for somethings to come out of earlier, and will be around for Satan to go into..and come out of again.
Just as in Job we see that God restrains the wicked powers as He sees fit, letting them go only so far, but restraining their power.
Cross reference these with Peter's statement on "Tartarus", a place of holding evil spirits, and it seems that we may have overlooked something here:
2Pe 2:4 For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment;
In the above verse the term "hell" is tartarus, a place of holding spirits.
Let me know what you find.
