So called, not from its situation in the tribe of Ephraim, which was on the other side Jordan, as is evident; but from some memorable action or occurrent of the Ephraimites beyond, Jordan; whether it was their killing of Oreb and Zeeb there, Judges 7:25, Judges 8:3, or their slaughter by Jephthah, Judges 12:5,6, or some other not mentioned in sacred Scripture.
Related Commentaries of 2 Samuel 18:6
2 Samuel 18:6
6 So the people went out into the field against Israel: and the battle was in the wood of Ephraim;