Can anyone religious answer me this about christenings?

It was a belief created by the Catholic Church. Before Christianity, Rabbis use to take groups of people to the nearest body of water to bathe before prayer service, as during those days, most people bathed once a month and prayer service would otherwise smell like a zoo. When Christianity emerged from Judaism, they took that custom, added some dogma and made it a Sacrament called Baptism. Christianity doesn't want Christians to know the history of their religion, only the dogma part.