This is very informative. My father was born in Madrid, Spain, and was brought up in Guadalajara, Jalisco in the forties and fifties. I have always wondered about the name, because it does sound Arabic. My father is Spanish-French, and does not think Sahagun is Arabic; he says it comes from the town of Sahagun, Spain, as a degeneration of the name San Facundo. What else have you found? I would be very interested in knowing more. As a sidenote, I have always been in love with Arabic music.
I live in Houston, TX, and will start a medical residency in Pediatrics.