After receiving the Davidic covenant, the LORD gave victory to David wherever he went. David defeated the Philistines and subdued them, and David took Metheg-ammah out of their hands. (2 Samuel 8:1)
What is it?
Scholars aren't sure what Metheg-ammah is. It only appears in this verse.
Some people think it refers to a piece of territory. Maybe it refers to a bridle of the mother-city, perhaps Gath or Ashdod. Some think the text is corrupted and irretrievable. Some think it refers to the cities from 1 Samuel 7:13-14. Some think Israel was not fighting the Philistines but the Zarephathites.
(Encyclopaedia Biblica: A Critical Dictionary of the Literary, Political, and Religious History: The Archaeology, Geography, and Natural History of the Bible. Volume III: L to P by Thomas Kelly Cheyne, John Sutherland Black, 1902. (Page 3064-3065), https://archive.org/details/encyclopaediabib03cheyuoft/page/n211/mode/2up (Page 212))