During the first four centuries, the Catholic Church was under intense persecution by the Roman Empire. To avoid persecution and the infiltration of pagans into the Church, every person who was received into the Church was required to have a sponsor.
During the first centuries, emphasis was placed on the baptism of adults. That all changed with the Council of Trent, (1545 - 1563)
In harmony with this new Decree and in consideration of the inability of an infant to speak for himself, more than ever, it became necessary to appoint a godparent who would make the Profession of Faith in the child's name. This same person would also be responsible for instructing the child in the faith, especially if the parents failed in their parental duty. I found this information on at the following website.For more details see link to Catholicdoors.com