§42. But small as this list seems to us the natural conservatism of the Romans found in it a chance to display itself, and the great families repeated the names of their children from generation to generation in such a way as to make the identification of the individual very difficult in modern times. Thus the Aemilii contented themselves with seven of these _praenomina_, _Gaius_, _Gnaeus_, _Lucius_, _Manius_, _Marcus_, _Quintus_, and _Tiberius_, but used in addition one that is not found in any other gens, _Mamercus_ (_MAM_). The Claudii used six, _Gaius_, _Decimus_, _Lucius_, _Publius_, _Tiberius_, and _Quintus_, with the additional name _Appius_ (_APP_), of Sabine origin, which they brought to Rome. The Cornelii used seven, _Aulus_, _Gnaeus_, _Lucius_, _Marcus_, _Publius_, _Servius_, and _Tiberius_. A still smaller number sufficed for the Julian gens, _Gaius_, _Lucius_, and _Sextus_, with the name _Vopiscus_, which went out of use in very early times. And even these selections were subject to further limitations. Thus, of the _gens Claudia_ only one branch (_stirps_), known as the _Claudii Nerones_, used the names _Decimus_ and _Tiberius_, and out of the seven names used in the _gens Cornelia_ the branch of the Scipios (_Cornelii Scipiones_) used only _Gnaeus_, _Lucius_, and _Publius_. Even after a _praenomen_ had found a place in a given family, it might be deliberately discarded: thus, the Claudii gave up the name _Lucius_ and the Manlii the name _Marcus_ on account of the disgrace brought upon their families by men who bore these names; and the Antonii never used the name _Marcus_ after the downfall of the famous triumvir, Marcus Antonius.
§43. From the list of names usual in his family the father gave one to his son on the ninth day after his birth, the _dies lustricus_. It was a custom then, one that seems natural enough in our own times, for the father to give his own _praenomen_ to his firstborn son; Cicero's name (§39) shows the name _Marcus_ four times repeated, and it is probable that he came from a long line of eldest sons. When these names were first given they must have been chosen with due regard to their etymological meanings and have had some relation to the circumstances attending the birth of the child: Livy in speaking of the mythical Silvius Aeneas gives us to understand that he received his first name because he was born in a forest (_silva_).