Smith’s Bible Dictionary
“Nephtoah” means opening
Nephtoah: The water of. The spring or source of the water or (inaccurately) waters of Nephtoah was one of the landmarks in the boundary line which separated Judah from Benjamin. (Joshua 15:9; 18:15) It lay northwest of Jerusalem in which direction, it seems to have been satisfactorily identified in Ain Lifta , a spring situated a little distance above the village of the same name.