Concise Bible Dictionary:

One of the early cities built by Asshur, or, probably by Nimrod, if we read “out of the land he (Nimrod) went forth to Assyria,” as in the margin (Gen. 10:11-1211Out of that land went forth Asshur, and builded Nineveh, and the city Rehoboth, and Calah, 12And Resen between Nineveh and Calah: the same is a great city. (Genesis 10:11‑12)). Supposed to be connected with some of the ruins on the Tigris, from which so many monuments and inscriptions have been discovered; but Calah cannot be distinguished from the other early cities mentioned in connection with Nimrod.

Strong’s Dictionary of Hebrew Words:

the same as 3624; Kelach, a place in Assyria: -Calah.

Jackson’s Dictionary of Scripture Proper Names:

full age

Potts’ Bible Proper Names:

Old age; maturity; favorable; completion:―place in Assyria [HALAH], Gen. 10:12. {Senectus}