Italian personae are very popular in the S. C. A., and as a consequence a fair number of Italian names (for individuals, associations, and awards) are submitted for registration with the S. C. A. College of Arms. Unfortunately, most of the people composing these names don't speak, read, or write Italian, and of those who do very few are familiar with any form of the language that was spoken before 1600. That results in a high percentage of submitted names that are improperly constructed and contain blatant grammatical errors.
The obvious way to avoid that is to use real medieval or Renaissance name phrases instead of making something up. The Medieval Names Archive guide to Italian Names and the S. C. A. College of Arms' articles on names from Italy have a wide variety of personal names, at least, from which you can choose. I strongly suggest starting there, if you want a name that connects to Italian history and cultural traditions. Names properly rooted in the period that interests you will always be a better reflection of that period than anything concocted by a mind with 21st-century predispositions and a limited understanding of the naming language.
If you do feel compelled to invent a name, there are resources to which you can turn to avoid the most glaring mistakes. The problem of English speakers not understanding how Italian works is not a new one. It inspired John Florio to add a detailed appendix on Italian grammar when he expanded his 1598 Italian/English dictionary, A Worlde of Words, into Queen Anna's New World of Words, published 11 years after the end of the S. C. A's period. It's a great resource on early-17th-century Italian. And as the fundamentals of a language typically change slowly, it can also help us make fairly solid guesses as to which prepositions, articles, and adjectives were compatible with which nouns in the 16th century and how they would have been combined.
In order to make it easier to read and cite, I have transcribed here, as faithfully as I could, the first dozen or so sections of the appendix. That included mimicking the alphabet used by Florio, which was a little different from the usual modern alphabet. While reading the transcript, remember that:
Two points not to forget: First, English has changed as much as Italian has in the past four centuries. When Florio explains the sound an Italian vowel makes by giving examples of English words containing the same sound, he's often not talking about the sounds you might assume. Check your favorite video repository for footage of actors doing OP (Original Pronunciation) performances of Shakespeare's works for an illustration. Second, Italian has dialects just as distinctive as those found in English, and they were (like the English dialects) even more different 400 years ago than they are now. Florio was certainly aware of these multiple forms of Italian. His dictionaries are notable for their inclusion of terms and definitions sourced from a variety of geographic and cultural settings.A But aside from an occasional brief comment—that a particular practice is more popular in Tuscany, for example—you won't see any discussion of dialectical differences within the appendix. If you want to construct a phrase perfectly suited to a specific part of the peninsula, you should do a little further research. The same goes for figuring out how a particular phrase would have been pronounced in a specific context.That said, I present to you several sections of: