Rev 17:5

5 and on her forehead a name written, “MYSTERY, BABYLON THE GREAT, THE MOTHER OF THE PROSTITUTES AND OF THE ABOMINATIONS OF THE EARTH.” 

on her forehead a name – this expression is used throughout Revelation. The number 666 “lateinos” is written on the forehead of those who worship the beast, and the saints have the name of God on their forehead.

Mystery – this is the spiritual kingdom of those who worship the beast, the false Christ. This kingdom of the beast continues today among those who exalt the teaching of the beast above the teachings of Christ.

Babylon – the Book of Daniel tells us the story of the kingdom of Babylon which took God’s chosen saints into captivity. The saints are again taken into captivity in mystery Babylon the Great, see Dan 7:25.

Babylon is described as a great tree such that the “birds come and nest in its branches” (Dan 4:12). This is the parable that Jesus used to describe the growth of the corrupted kingdom of heaven, in Matt 13:32. In Daniel, we are told that the tree will be cut down but only the stump will remain, (Dan 4:15). In other words, the corruption will be removed and the tree will be restarted from the stump, with “a band of brass and iron around it.” (The band of brass and iron prevents a tree from growing without killing it, allowing it to grow later when desired.)

King Nebuchadnezzar was made as “a beast” to eat grass, until he learned “that the most High rules in the kingdom of men.” Because he “exalted himself,” (compare Dan 5:21 to Dan 11:36), Babylon became “the kingdom of the beast.”

As the king of Babylon, Nebuchadnezzar was made the head of the statue of the four kingdoms (Dan 2:38), which became “seven kingdoms” in the Book of Revelation. These are the “seven heads” on which the woman sits.

The Great – three “great” kingdoms are explained in Dan 8. The first, belonging to the ram, in Dan 8:4, who “magnified himself” – this was the kingdom of Persia, typified by “Cyrus the Great.” The second belonging to the goat, in Dan 8:8, who “magnified himself exceedingly, typified by “Alexander the Great.” The final kingdom, in Daniel 8:9, “which grew exceedingly great” is “mystery Babylon the Great.”

the mother of harlots – the Catholic Church grew until the Reformation and became the “mother of harlots” – the mother of many denominations that hung onto a mixture of pagan religious practices and the teachings of Christ. This harlotry was described by Hosea: “they turn to other gods and love the raisin cakes (of the pagans)” (Hosea 3:1). The mother of Hosea’s harlotrous wife was actually named “Diblaim,” meaning “two cakes.”

and the abominations of the earth– virtually all of the significant deviations from the truth come from the 42 month period of 193 to 1471.