I think you are referring to patron saints…
13 And I heard a voice from heaven saying, “Write this: Blessed are the dead who die in the Lord henceforth.” “Blessed indeed,” says the Spirit, “that they may rest from their labors, for their deeds follow them!”
How Patron Saints Are Chosen
Thus, the patron saints of churches, and more broadly of regions and countries, have generally been chosen because of some connection of that saint to that place—he had preached the Gospel there; he had died there; some or all of his relics had been transferred there. As Christianity spread to areas with few martyrs or canonized saints, it became common to dedicate a church to a saint whose relics were placed in it or who was especially venerated by the founders of the church. Thus, in the United States, immigrants often chose as patrons the saints that had been venerated in their native lands.
Patron Saints for Occupations
As the Catholic Encyclopedia notes, by the Middle Ages, the practice of adopting patron saints had spread beyond churches to “the ordinary interests of life, his health, and family, trade, maladies, and perils, his death, his city and country. The whole social life of the Catholic world before the Reformation was animated with the idea of protection from the citizens of heaven.” Thus, Saint Joseph became the patron saint of carpenters; Saint Cecilia, of musicians; etc. Saints were usually chosen as patrons of occupations that they had actually held or that they had patronized during their lives.