E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The founder of the illustrious house which was so conspicuous in the fifteenth and sixteenth centuries, was the son of a day-labourer. His name was Giacomuzzo Attendolo, changed to Sforza from the following incident:Being desirous of going to the wars, he consulted his hatchet thus: he flung it against a tree, saying, If it sticks fast, I will go.It did stick fast, and he enlisted. It was because he threw it with such amazing force that he was called Sforza, the Italian for force.
Sforza (in Jerusalem Delivered) of Lombardy. He, with his two brothers, Achilies and Palamedes, were in the squadron of adventurers in the allied Christian army.