Nirgal (H7331) is a Babylonian deity — the god of war, pestilence, and the underworld — whose name was incorporated into the names of Babylonian officials (Nergal-sharezer, Jer 39:3,13) and colonists who settled in Samaria after the Assyrian exile (2 Kgs 17:30). The Cutheans who settled in Samaria 'made Nergal' their god — a sobering reminder of how foreign culture and religion fill the vacuum left by displaced people.
The appearance of Nergal in Scripture serves as a theological foil: the gods of the nations are nothing (Ps 96:5, Isa 41:24), while YHWH is Lord over pestilence, death, and war. Nergal was feared as the god who could bring plague and death — but it is YHWH who 'kills and makes alive' (Deut 32:39), who holds the keys of death and Hades (Rev 1:18). The Babylonian colonists' worship of Nergal in the promised land represents the syncretism God had always warned against, and the tragic consequences of covenant unfaithfulness.