(I goofed and added the plural.) Nickname for storm petrels. Mother Carey is thought to be a corruption of Mater Cara, one of the epithets of Mary, the mother of Christ. The term was used by early Spanish and Portuguese sailors in the southern seas. Storm petrels were known as "sailors' friends" that warned them of approaching storms. It was considered extremely unlucky to kill them, since each bird contained the soul of a dead seaman.