The city of Uruk was known by the lovely name of
Tiranna, the
Rainbow City, in the
Seleucid period (after the death of
Alexander the Great). I have no idea why nor whether it has any reference to the rainbow seen by the
Flood hero.
The great temple at Uruk was called the Eanna, from e-anna 'house of heaven', so the city was sometimes called 'the sheepfold of Eanna'.
The word uruk is also the evil Black Speech name for orc or goblin, in the works of J.R.R. Tolkien. The elite breed from Mordor were called the Uruk-hai. The name is of course a borrowing from the Elvish: the proto-Elvish root is órok-, from which comes old Noldorin orko, Sindarin orch (plural yrch), and Ilkorin urch (dialect of Doriath).