Fausset's Bible Dictionary
Of the Chaldees (Genesis 11:28; Genesis 11:31; Genesis 15:7; Nehemiah 9:7), from which Terah, Abraham, and Lot were called. In Mesopotamia (Acts 7:2). Now Mugheir (a ruined temple of large bitumen bricks, which also "mugheir" means, namely, Um Mugheir "mother of bitumen"), on the right bank of the Euphrates, near its junction with the Shat el Hie from the Tigris; in Chaldaea proper. Called Hur by the natives, and on monuments Ur. The most ancient city of the older Chaldaea. Its bricks bear the name of the earliest monumental kings, "Urukh king of Ur"; his kingdom extended as far N. as Niffer. The royal lists on the monuments enumerate Babylonian kings from Urukh (2230 B.C., possibly the Orchanus of Ovid, Met. 4:212) down to Nabonid (540 B.C.) the last. The temple was sacred to 'Urki, the moon goddess; Ilgi son of Urukh completed it.
For two centuries it was the capital, and always was held sacred. One district was "Ibra," perhaps related to "Hebrew," Abraham's designation. Ur was also a cemetery and city of tombs, doubtless because of its sacred character, from whence the dead were brought to it from vast distances for 1,800 years. Eupolemos (in Eusebius, Praep. Ev. 9:17) refers to Ur as "the moon worshipping (kamarine; kamar being Arabic for moon) city." The derivation from Ur, "fire," led to the Koran and Talmud legends that Abraham miraculously escaped out of the flames into which Nimrod or other idolatrous persecutors threw him.
Ur lies six miles distant from the present coarse of the Euphrates, and 125 from the sea; though it is thought it was anciently a maritime town, and that its present inland site is due to the accumulation of alluvium (?). The buildings are of the most archaic kind, consisting of low mounds enclosed within an enceinte, on most sides perfect, an oval space 1,000 yards long by 800 broad. The temple is thoroughly Chaldaean in type, in stages of which two remain, of brick partly sunburnt, partly baked, cemented with bitumen.
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Fausset, Andrew R. Entry for 'Ur'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/u/ur.html. 1949.