According to the Music for Living - Book Six - Around the World the California State Series Pulbished by the California State Department of Education, Scaramento, 1958 p.210-211 (a book series discussed in an unrealated thread last week, still looking for book three)

"This ancient folk song is probably from the Hebrew." "The words of this song are symbolic; the meaning of these symbols has been corrupted over long years of use. In general, "One" was meant to be God Almighty, "Two", Christ and John the Baptist. "ThreeT is the Holy Trinity, "Four" is the four disciples of Christ - Mathew, Mark, Luke, and John. "Five" is the five pointed star used in olden times to keep away evil spirits. "Six" is for the corruption of waters, a reference to the water-pots in the miracle of changin water to wine. "Seven" is the stars of the Great Bear, "Eight" refers to Gabriel and archangels, "Nine" to the nine muses, "Ten" to the Commandments, "Eleven' is for Judas Iscariot and "Twelve" sums up the twelve apostles"

The significance of the pentagram/star to ward off evil is found in the stigmata based this link to a course at Dartmouth University:Number Symbolism in the Middle Ages