Easton's Bible Dictionary (1897)
Multitude of Gog, the name of the valley in which the slaughtered forces of Gog are to be buried (Ezek. 39:11, 15), “the valley of the passengers on the east of the sea.”
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
HA'MON-GOG (multitude of Gog), a name given to a ravine or valley in which multitudes of the slain of Gog were to be buried, Eze 39:11, Eze 39:15. The Targums regard it as near the Sea of Galilee, and probably on the great road from Syria and the East to Egypt.
Hitchcock's Bible Names (1869)
the multitude of Gog