Fausset's Bible Dictionary
The Egyptian king to whom Hoshea, Israel's last king, applied in the ninth year of his reign for help, when casting off the obligation to pay tribute to Assyria (2 Kings 17:4). So did not venture to encounter the Assyrian king Shalmaneser, but deserted his protege, as Egyptian kings often did (Isaiah 30:3; Isaiah 36:6). Israel was conquered and Samaria taken. Egyptian monuments illustrate Scripture; precisely in Hoshea's time a change occurs in the Egyptian dynasties. Manetho's 25th or Ethiopian dynasty extended its influence into Lower Egypt in 725 B.C.
So or Seveh answers to "Sabacho" of Manetho, and "Shebek I" of the hieroglyphics. A little later So contended with Sargon in southern Palestine. A seal of fine clay, impressed from the bezel of a metallic finger ring, an oval two inches long by one wide, bears the image, name, and titles of Sabacho. Some make So the first Sabacho, others Sabacho II. Tirhakah or Tehrak, the third and last of the dynasty, is thought to have put So to death. Sabaku (according to G. Smith's deciphering) married the sister of Tirhakah who helped Hezekiah against Sennacherib; at Sabaku's death Tirhakah succeeded, Sabaku's son being set aside.
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Fausset, Andrew R. Entry for 'So'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/s/so.html. 1949.