The Hebrew zenut (H2184) is the abstract noun from zanah (to commit fornication/play the harlot). It describes sexual immorality but more often, in the prophets, Israel's spiritual adultery β abandoning covenant loyalty to God for the pursuit of idols. In Ezekiel 23, both Samaria and Jerusalem are condemned for their zenut β the spiritual prostitution of covenant-breaking. Hosea's entire prophetic ministry was built on this metaphor.
The prophets, especially Hosea, Jeremiah, and Ezekiel, develop zenut as the primary metaphor for apostasy. The covenant between God and Israel was marriage-like in its exclusivity and intimacy (cf. Hosea 2). Any turning to other gods was therefore adultery β a zenut that broke the covenant bond. This prophetic tradition is why Revelation speaks of 'Babylon the Great, the mother of prostitutes' (porneion β Rev 17:5): it represents the anti-covenant world system that seduces the people of God away from their true Husband.