Gomorrah appears in the Hebrew Bible more than twenty times and almost never alone. It has a king of its own in the account of the war of the kings in Genesis 14, and it stands with Sodom in the description of the well watered plain that Lot chooses, in the destruction narrative, and thereafter in a long series of prophetic warnings: Deuteronomy on a land laid waste, Isaiah on rulers and on the overthrow of Babylon, Jeremiah on Edom and on Babylon again, Amos on a city God overthrew, Zephaniah on Moab and Ammon. The New Testament keeps the pairing in the gospels and the letters, and Paul quotes Isaiah's line that but for a remnant Israel would have become like Sodom and Gomorrah.
The Quran tells the story of Lut and his people at length without naming the cities, referring instead to the townships that were overthrown.
The cities of the plain are in fact a group of five, with Admah, Zeboiim and Zoar named alongside the other two, and Zoar spared at Lot's request. Hosea preserves a variant in which the pair invoked is Admah and Zeboiim rather than Sodom and Gomorrah, which suggests that the standard pairing was one tradition among several before it became fixed.
The consistency of the pairing across a thousand years of writing is itself the point. By the time of the prophets the two names had fused into a single figure of speech for a place wiped out and left uninhabited, and a writer reaching for it was invoking a formula rather than describing a town he could have walked to.