Curst cows have curt horns. Angry men cannot do all the mischief they wish. Curst means “angry” or “fierce,” and curt is “short,” as curtmantle, curt-hose. The Latin proverb is, “Dat Deus immiti cornua curta bovi. ”
You are called plain Kate, And bonny Kate, and sometimes Kate the curst.
Shakespeare: Taming of the Shrew, ii. 1.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894