After publishing a new Qatabanic inscription that mentions the term kʿbt for the first time, this paper provides a South Arabian etymology for the pre-Islamic Meccan sanctuary of the Kaʿbah, which is derived traditionally from the Arabic word kaʿb “cube”. The paper suggests that the name of the Meccan Kaʿbah, and the Kaʿbah of Najrān, both derived from the ancient South Arabian term kʿbt, supposedly as a variant of the term kʾbt, which designates a high structure, probably with a protective function against water, a term which was later assigned to a sanctuary name for the deity dhu-Samāwī in Najrān; and not derived from Arabic kaʿb “cube”. The paper argues that the Arabic word “kaʿb” meaning “cube” was borrowed from Greek κύβος at a later time after the Meccan Kaʿbah had already established the cubic form that we know today.