How do Latin names work? I don't know why I'm so confused. I thought my whole life names like Titus and Augustus were the original names, but the inscriptions on Roman monuments are Tito and Augusto and Septimio etc. Are those the originals (how they were referred to back in ancient Rome), and the -us suffix we use just an Anglicization of it?
It has to do with Latin declensions and cases (something we don't have in English). In Latin, the end of a noun is modified depending on its role in the sentence (whether it's the subject, the object, etc.). Titus would be the actual name; Tito would be a genetive or dative case ("To the glory of Titus"). But my Latin is rusty: another redditor will likely have a more in-depth answer
As other respondents have pointed out, nouns change depending on how they are used in the sentence. English has this for pronouns; HE, HIS and HIM are sort of the same word and vary on how it is used.
Do you have the full inscription? Is it a in a sentence?
Was this in Italy? Tito is the Italian for the Latin Titus.