David took Metheg-ammah - This is variously translated. The Vulgate has, Tulit David fraenum tributi, David removed the bondage of the tribute, which the Israelites paid to the Philistines. Some think it means a fortress, city, or strong town; but no such place as Metheg-ammah is known. Probably the Vulgate is nearest the truth. The versions are all different. See the following comparison of the principal passages here collated with the parallel place in 1 Chr: -
2 Samuel 1 Chronicles 2 Samuel 8:1. - David took Metheg-ammah 2 Samuel 8:3. David 1 Chronicles 18:1. - David took Gath and her towns. 1 Chronicles 18:3. David smote Hadadezer 2 Samuel 8:4. And David took from him smote Hadarezer 1 Chronicles 18:4. And David took from him 1000 and 700 horsemen, and 20,000 foot. 1000 chariots, and 7000 horsemen, and 20,000 foot. 2 Samuel 8:6. Then David put garrisons in Syria 2 Samuel 8:8. And 1 Chronicles 18:6. Then David put in Syria 1 Chronicles 18:8. And from Betah and Berothai cities of Hadadezer. 2 Samuel 8:9. from Tibhath and Chun cities of Hadarezer. 1 Chronicles 18:9. When Toi heard that David had smitten When Tou heard that David had smitten Hadadezer 2 Samuel 8:10. Then Toi sent Joram his son Hadarezer 1 Chronicles 18:10. He sent Hadoram his son 2 Samuel 8:12; Syria and Moab 2 Samuel 8:13. - Syrians, in the valley 1 Chronicles 18:11; Edom and Moab 1 Chronicles 18:12. - Edomites, in the valley of salt, 18,000 2 Samuel 8:17. - Ahimelech - and Seraiah of salt, 18,000 1 Chronicles 18:16. - Abimelech - and Shausha was the scribe. 2 Samuel 10:16. Shobach the captain was scribe. 1 Chronicles 19:16. Shophach the captain 2 Samuel 10:17. David passed over Jordan, and came הלאמה 1 Chronicles 19:17. David passed over Jordan and came אלהם to Helam. 2 Samuel 10:18. David slew 700 upon them 1 Chronicles 19:18. David slew of the Syrians 7000 chariots of the Syrians, and 40,000 horsemen; chariots, and 40,000 footmen; and smote Shobach, etc. and killed Shophach, etc.
Metheg-ammah must be the name of some stronghold which commanded Gath, and the taking of which made David master of Gath and her towns.