The excellent posts so far have pretty much answered the question. To fill in, the ancient Romans had a naming system for men (the only people who counted). A man had 3 names, as noted in the example cited in Bill's post: the praenomen e.g., Marcus; the nomen e.g., Tullius; the cognomen e.g. Cicero. There were only a small number of praenomines, so they were often abbreviated, like M. for Marcus. The cognomen was, as noted, a family name, so one's personal name was the one in the middle, which is why a good many writers used to refer to M. Tullius Cicero as Tully (the 'y' ending being an Anglicization). Cicero referred to himself as Marcus Tullius -- in the oration (In Catalinam}which has been quoted in the Latin Translation thread, he said, "If the Fatherland should say to me, 'Marce Tulle, quid agis?'" (the name here being declined with the endings for the vocative case).
