'Fierceness' in the Bible

And there shall cleave nought of the cursed thing to thine hand: that the LORD may turn from the fierceness of his anger, and shew thee mercy, and have compassion upon thee, and multiply thee, as he hath sworn unto thy fathers;

And all the nations will say, '{Why} has Yahweh done {such a thing} to this land? What [caused] the fierceness of this great anger?'