Purgatory

Purgatory noun (Middle English, from Anglo-French purgatorie, from Medieval Latin purgatorium, from Late Latin, neuter of purgatorius purging, from Latin purgare)
1): an intermediate state after death for expiatory purification
2): place or state of temporary suffering or misery

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Purgatory,according Purgatory, according to Christian doctrine, is the place where souls wted until the coming of Christ.

According to the Jewish Encyclopedia: Hell (sheol) is the abode of all the dead, and was viewed as divided into four  parts, two for the righteous and two for the bad. The most righteous is known as Abraham's Bosom. The two lowest are known as Prison (i.e. Purgatory).

The Bible references to prison:
Christ . . .also suffered once for sins, the just for the unjust, that He might bring us to God, being put to death in the flesh but made alive by the Spirit, by whom also He went and preached to the spirits in prison, who formerly were disobedient, when once the Divine longsuffering waited in the days of Noah
I Peter 3:18 

The parable of the Rich Man and Lazarus in John 5:39-47 At death they found themselves in two divisions of the same place. Lazarus was in The Bosom of Abraham (Paradise) and the rich man was in another division of Hell. They  could see each other and they were within speaking distance


All the saints . . . said to the prince of hell, Open now thy gates, and take away thine iron bars; for thou wilt now be bound, and have no power . . . And the mighty Lord appeared in the form of a man, and enlightened those places which had ever before been in darkness, And broke asunder the fetters which before could not be broken; and with his invincible power visited those who sate in the deep darkness by iniquity, and the shadow of death by sin. Then the prince of hell said, He has broke down our prisons from top to bottom, dismissed all the captives, released all who were bound, and all who were wont formerly to groan under the weight of their torments have now insulted us, and we are like to be defeated by their prayers. Then Jesus stretched forth his hand, and said, Come to me, all ye my saints, who were created in my image, who were condemned by the tree of forbidden fruit, and by the devil and death. - The Apocryphal Gospel of Nicodem:

Purgatory is simply another word for the prison in Hell. Catholic tradition has misinterpreted thngs and rather than referring to the prison in Hell, they have created an entirely new place that fulfills the same purpose.