In history, Christmas has started in Greek and Roman Empire to honor the god, Saturn who is a cannibal giant who eats humans. In that time, December festivities were called Saturnalia.
youtube.com/watch?v=mvURMFzcIqc
Later on, the custom of Saturnalia (=Christmas) changed. People started giving a gift to not only the cannibal god, Saturn (human sacrifice gift) but also to people. That is the custom of Christmas giving a gift to everybody.
