My dissertation seeks to understand why Marduk, the chief god of ancient Babylon, was often also called ‘Bēl’ (which means ‘lord’). Although this matter has never been investigated, a consensus seems to have formed in the field that ‘lord’ is an appropriate by-name for a chief god, and that the two names were used interchangeably. My research however has shown that the two assumptions on which the consensus rests are incorrect, and puts forward a new framework for understanding the function of these names. By consulting numerous assemblages of primary sources of different types and from both Babylonia and Assyria, I have been able to identify a distribution in the usage of the two names which not only sheds light on this particular case, but also goes to the heart of Mesopotamian concepts of divinity.

Primarily - although there is significant variation across time and between Babylonia and Assyria - I show that, while the name ‘Marduk’ was used to refer to the god in all of his roles – as a god of magic, as a warrior, a creator, the patron deity of Babylon, and the king of gods etc. – the name ‘Bēl’ was primarily only used for the god when playing the role of patron deity of Babylon. I also show that while the name ‘Marduk’ was used for the god in any of his manifestations – as an ethereal being, a planet in the sky, a statue in a temple, or in the form of his ‘symbol,’ the spade – the name ‘Bēl’ was primarily only used for the god when manifested in his primary statue in Babylon. My dissertation further examines the implications of this distribution.