1) Christening observance 2) Date of baptism 3) It honors a saint 4) Patronal feast 
A name day is a tradition in many countries in Europe and Latin America that consists of celebrating the day of the year associated with one`s given name. The custom originated with the Christian calendar of saints: believers named after a saint would celebrate that saint`s feast day. In many countries, however, there is no longer any explicit c.....
(from the article `Christianity`) ...a Christian generally received the name of the saint on whose holiday (day of death) he is baptized. The believer was thus joined for life with ...
[n] - the feast day of a saint whose name one bears
noun the feast day of a saint whose name one bears
the feast day of the saint after whom a person is named. · the day on which a person is christened.