A king of Egypt, mentioned once in Scripture (2 Kgs 17:4), with whom Hoshea, king of Israel, sought an alliance. This rebellious move, in part, prompted Shalmaneser V of Assyria to imprison Hoshea (2 Kgs 17:3–5). It is difficult to identify So with any of the rulers of Egypt who are named in extrabiblical sources.
So
From Tyndale Bible Dictionary, adapted by Mission Mutual. CC BY-SA 4.0.