The Element Encyclopedia of Witchcraft: The Complete A-Z for the Entire Magical World - Judika Illes 2005
The Horned One and The Devil
Se’irim (singular: se’ir) are goat-shaped Semitic spirits. Their name derives from sai’ir or “hairy” or “shaggy.” In Leviticus 17: 7, Jews are forbidden to sacrifice to them, which of course indicates that some were following this practice, necessitating legislation against it.
It is possible that the medieval image of the devil goes back to the Se’irim. The word has come to mean “goat” but also “devil.”
See also Azazel.