Dies lustricus

In ancient Rome the dies lustricus ("day of lustration" or "purification day") was a traditional naming ceremony in which an infant was purified and given a "praenomen" (given name). This occurred on the eighth day for girls and the ninth day for boys, a difference Plutarch explains by noting that "it is a fact that the female grows up, and attains maturity and perfection before the male." Until the umbilical cord fell off, typically on the seventh day, the baby was regarded as "more like a plant than an animal," as Plutarch expresses it. The ceremony of the "dies lustricus" was thus postponed until the last tangible connection to the mother's body was dissolved, and the child was seen "as no longer forming part of the mother, and in this way as possessing an independent existence which justified its receiving a name of its own and therefore a fate of its own." The day was celebrated with a family feast. The childhood goddess Nundina presides over the event, and the goddess Nona was supposed to determine a person's lifespan. Prior to the ceremony infants were not considered part of the household, even if their father had raised them up during a "tollere liberum".
On the "dies lustricus", the "Fata Scribunda" were invoked. The "Written Fates" probably refers to a ceremonial writing down of the child's new name, perhaps in a family chronicle. To the Romans, the giving of a name was as important as being born. The receiving of a "praenomen" inaugurated the child as an individual with its own fate. A child's name may have been decided on before hand in the preceding days. In rare instances children were given names before the ceremony, for example one child named Simplicius is recorded to have died the same day as he was born, possibly only living an hour.
The day may also have been when the child received the "bulla", the protective amulet that was put aside when a boy passed into adulthood. The practice was widespread in the Western Roman Empire into late antiquity. This tradition was familiar to Christians as well whom seem to have incorporated parts of it into their own lives.