Derived from the root m-l-ʾ ('to fill'), Millo designates a massive filled earthwork or stone terrace that served as a fortification. Two distinct structures bear this name: one near Shechem, called bêth millôʾ ('house of Millo,' Judg 9:6, 20), associated with the Shechemite aristocracy in the Abimelech narrative; and the more famous Millo in Jerusalem, a major engineering project that David built up after capturing the city (2 Sam 5:9) and Solomon later strengthened (1 Kgs 9:15, 24; 11:27). The Akkadian cognate mulû ('earthwork, mound') confirms the architectural meaning. King Joash was assassinated at bêth millōʾ (2 Kgs 12:21), showing its continued importance centuries later.