Wikipedia
Decimus may refer to:
Decimus is a Latin praenomen, or personal name, usually abbreviated D. Although never especially common, Decimus was used throughout Roman history from the earliest times to the end of the Western Empire and beyond, surviving into modern times. The feminine form is Decima. The name also gave rise to the patronymic gens Decimia.
Decimus was especially favored by the plebeian gens Junia, which may originally have been patrician. However, the name does not seem to have been used regularly by any other patrician family. It was widespread amongst the plebeians, and resisted the general trend of uncommon praenomina to become less frequent over time, instead becoming more popular towards the end of the Roman Republic and into Imperial times.