Abimelech in Fausset's Bible Dictionary

("father of a king", or "father king".) A common title of many Philistine kings, as Pharaoh of the Egyptians, and Caesar and Augustus of the Roman: Padishah (father king) is similarly a title of the Persian king. 1. Hence, we find Achish called Abimelech in the title of Psalm 34, which explains the seeming discrepancy of name in 1 Samuel 21:11. 2. Genesis 20:1, 1898 B.C.; Hales, 2054 B.C.: the king of Gerar. Abimelech's taking Sarah into his harem shows that in those times kings claimed the odious despotic right of taking unmarried females, whether subjects or sojourners; compare Genesis 12:15; Esther 2:3. A divine warning that death would be the penalty of keeping her, but that Abraham's intercession as a prophet would follow the restoring of her, led him to give her back with a present of a thousand pieces of silver (131 British pounds). With delicate sarcasm (in the English KJV) he reproved Abraham's deception...

Link: https://bible-history.com/faussets/A/Abimelech/