Bridle of the mother, a figurative name for a chief city, as in 2 Sam. 8:1, "David took Metheg-ammah out of the hand of the Philistines" (R.V., "took the bridle of the mother-city"); i.e., subdued their capital or strongest city, viz., Gath (1 Chr. 18:1).
Easton's Bible Dictionary. M.G. Easton. 1897.