Singular masculine Italian words often end in the letter ‘o’. When you pluralize those words the ‘o’ is switched to an ‘i’.
For example, Concerti would be the Italian pluralization of a Concerto.
Nonno (grandfather) becomes Nonni (grandfathers, or grandparents).
Presumably then I am a DiDonato but together my family are DiDonati
Extra credit: Feminine words end in ‘a’ and their plural end in ‘e’. That means you might have a pizza tonight, or you might have four pizze tonight.
Double extra credit: Why is the word ‘beer’ feminine and the word ‘wine’ masculine in the romance languages? This seems backwards to stereotypical beverage choice.
Other language varieties don’t contain the same gender choices, for example I think Irish languages have both beverages as masculine.
There’s a pretty good wikipedia article on grammatical gender that explains some forms of gender origination, but as to how these particular words claimed their gender? I haven’t a clue.