A Roman male had a three-part name. The official equivalent to our first name was the praenomen, but there were only about twenty of those in regular use. Common praenomens (or praenomina to give the correct Latin plural) included Gaius, Lucius, Marcus, Publius, Quintus, Sextus, and Titus.

The nomen was a family name. The cognomen was originally a nickname, but it became hereditary as well - a nomen would belong to a large clan, and then a cognomen would belong to a smaller family within that clan.

Most infamous names such as Catiline, Caligula, Nero, or Commodus were cognomina or sometimes even additional names, so they would not have been given to children as first names.

Women were only named after the feminine form of their father's nomen (e.g., Julia for a female of the Julius family), and daughters of the same family were numbered. But they later sometimes had additional nicknames as well.