Boyd’s Bible Dictionary:

(as demons). The country lying along the Euphrates on both sides, and between it and the Tigris, for three or four hundred miles back from their mouths (Gen. 10:10; 11:31; Job 1:17).

Concise Bible Dictionary:

This was strictly the southern part of Babylonia, but the many references in scripture to the Chaldeans show that the inhabitants of the whole of Babylonia are alluded to by that name. Perhaps Ur is the only place in Chaldea proper to which scripture definitely refers. This was apparently a maritime city, which agrees with the country extending to the Persian Gulf; but the Gulf has receded far from where the river once joined it. The land of Shinar adjoined Chaldea on the north, in which were the early cities of Babel, Erech, Accad and Calneh (Gen. 10:10). The whole district was situated between the rivers Tigris and the Euphrates, but extended west of the latter. It was anciently well watered by canals, and is judged to have been productive. Herodotus says mounds were built where the river once spread like a sea through the whole plain. Now all is desolation, some parts very dry, and others a mere swamp, with lines of mounds in various directions. The prophecies declared that it would be so, but as stated above, they refer to the whole of Babylonia (Jer. 1:10; Jer. 51:24, 35; Ezek. 11:24; Ezek. 16:29; Ezek. 23:15-16).

Jackson’s Dictionary of Scripture Proper Names:

as clod-breakers