Hastings' Dictionary of the Bible (1898)
MIXED MULTITUDE, an expression occurring Ex 12:38; Num 11:4, and Neh 13:3, and denoting people who congregated with the Israelites without being of pure Israelite blood. By some it is explained as referring to the offspring of mixed marriages between Israelites and those nations among which they lived; by others as referring simply to those hangers - on who are always found hovering on the outskirts of a great camp.