c.1300, from O.Fr. force, from L.L. fortia, from neut. pl. of L. fortis "strong"
So, Latin to French to Italian.
[Italian, gerund of sforzare, to use force : s-, intensive pref. (from Latin ex-; see ex-) + forzare, to force (from Vulgar Latin *fortiāre, from Latin fortis, strong; see fortis).]
That's the etymology of "force," not sforzando.French isn't an element in the etymology of the modern Italian word sforzando:(From The American HeritageŽ Dictionary of the English Language, Fourth Edition (at dictionary.com).)While a multitude of words passed into English from Old French following the Norman invasion, Italian evolved directly from local varieties of Vulgar Latin. "Force" is derived from Old French; sforzando, like much of classical music's technical vocabulary, is a loanword directly from Italian.