Obviously the meaning on this is all muddy, but here's what I could find with a little digging and it seems plausible "The pentacle of Satanism is an inverted pentagram, meant to represent the head of a goat (Satan is often portrayed in mythical drawings as a man with a goat's head.) The two upward-facing points are meant to resemble the horns of a goat, the sideways-facing points are ears, while the downward-facing point is the muzzle. Some schools of Satanism use the three downward-facing points to represent the rejection of the Holy Trinity of Christianity -- the Father, Son and Holy Ghost." Also, to note as somebody kindly pointed out, this is a pentacle, and not an upside down one like satanists would typically use, so it could either be very subtle, pagan in origin, or just our brains reading into things.

A pentacle was the symbol of Celtic religion, as the Cross is to Christians. Carried by Druids (the learned, priest class), It stood for harmony of the five elements; always pointed up to heaven; signifying wisdom.

The pentagram is a perversion, invented as a satanic symbol by Anton Szandor LaVey, along with the inverted cross. Earlier, it was used by Wicca; itself a perversion of Druidism. They cannot create, they can only pervert and desecrate the holy.