The Syrians called him that.
The servants of the king of Syria said unto him, Their gods are gods of the hills; therefore they were stronger than we; but let us fight against them in the plain, and surely we shall be stronger than they. 1 Kings 20.23Then an anonymous "man of God" told the king of Israel (Ahab) that God would slaughter the Syrians for calling him a hill god and, by so doing, show Ahab that he is the Lord.
There came a man of God, and spake unto the king of Israel, and said, Thus saith the LORD, Because the Syrians have said, The LORD is God of the hills, but he is not God of the valleys, therefore will I deliver all this great multitude into thine hand, and ye shall know that I am the LORD. 20.28So God delivered the Syrians into Ahab's hand and the Israelites killed 100,000 in one day.
And the children of Israel slew of the Syrians an hundred thousand footmen in one day. 20.29(That's about twice as many as were killed in the three-day Battle of Gettysburg. But then, God wasn't involved in that one. He couldn't make up his mind which side he was on.)
God's next killing: God killed 27,000 Syrians with a falling wall