Latin word propterea comes from Latin propter, Latin ea

Detailed word origin of propterea

Dictionary entry	Language	Definition
propter	Latin (lat)	Near, at hand, hard by (rare) through, by means of. Because of, on account of, for. Near, close to, hard by.
ea	Latin (lat)	On that side. That way. There Accusative neuter plural of is: "them (things)". Nominative feminine singular of is: "she", "it" (referring to feminine nouns). Nominative neuter plural of is: "they (things)".
propterea	Latin (lat)	Therefore; for that reason.