Chaldea was the name of the land in southern Babylonia. The term was later used to denote Babylonia as a whole, especially during the last dynasty of Babylonia (626-539 B.C.).
When Mardukapla-iddina II (Merodach-Baladan), the chief of the Chaldean district of Bit-Yakin, seized the throne of Babylon in 721-710 and 703-702 B.C. he sought help from the west against Assyria (Isaiah 39). The prophet Isaiah warned of the danger to Judah of supporting the Chaldean rebels (Isaiah 23:13) and foresaw their defeat Isaiah 43:14), perhaps after the initial invasion by Sargon in 710 B.C. Since Babylon was at this time under a Chaldean king, "Chaldean" is used as a synonym for Babylonian (Isaiah 13:19; 47:1,5; 48:14,20), a use later extended by Ezekiel to cover all the Babylonian dominions (Ezekiel 23:23). [Tyndale House, The Illustrated Bible Dictionary, Vol. 1, pp. 257-258] [See the commentary on 1 Nephi 20:14]
2 Nephi 23:19 Chaldees ([Illustration]): Chaldea: a name for part of Babylonia taken over for the whole land in 8th and 7th centuries B.C. [Tyndale House, The Illustrated Bible Dictionary, Vol. 1, p. 257]