In classical Greek abyssos was an adjective meaning “bottomless,” applied to the primeval deep of ancient cosmogonies, an ocean surrounding and under the earth. In the LXX it translates Hebrew tehôm, meaning the primal waters of Gen.1.2; once the world of the dead (Ps.71.20). In later Judaism it means also the interior depths of the earth and the prison of evil spirits.
The use of abyss in Rom.10.7 is parallel with the use of “the lower, earthly regions” in Eph.4.9 (see Ps.106.28); both contrast the highest heaven and the lowest depth. In Luke.8.31 the demons had a great dread of the primal abyss; even so, they may have caused themselves to go there when the pigs were drowned in the sea. In Revelation the horror of infinite deeps is intensified.——ER
Classical writers used the word to describe things so deep or great as to be without measure, such as pools, fountains, and wealth. It occurs frequently in the LXX, usually translating the Heb. תְּהוֹם, H9333, to signify the great ocean depths (e.g. Ps 33:7; 107:26). In Genesis 1:2 it also represents תְּהוֹם, H9333, referring to the primeval sea.
In Hel. times the concept of the underworld was suitably expressed by the same word. Its application in Luke 8:31 to the place to which the demons are loath to go, is understandable. Some see a connection with the spirit prison described in 2 Peter 2:4 and Jude 6, though the word “abyss” is not used. Care is necessary, of course, lest non-Christian concepts of the underworld govern the interpretation of the NT. It refers to the state or place of Christ in death (Rom 10:7). (Deut 30:12 f., from which the v. is adapted has the word יָם, H3542, “sea.”)
The passages in Revelation describe the abyss as an abode of evil beings. In Revelation 9:1-12 evil creatures, whose king is “Destroyer,” proceed from the pit. The abyss is also mentioned in Revelation 17:8 as the place from which the beast who bears the harlot Babylon arises. It is the location of Satan’s confinement for one thousand years (20:1, 3). The varied uses of the term in Jewish, pagan and Christian lit. have in common the idea of an immense and terrifying place, though the specific applications differ according to context.
LSJ, s.v.; Arndt, s.v.; TDNT, I, s.v.
International Standard Bible Encyclopedia (1915)
a-bis’, (he abussos): In classical Greek the word is always an adjective, and is used
(1) literally, "very deep," "bottomless";
See also ASTRONOMY, sec. III, 7.