why is snape the half blood prince

Severus Snape calls himself the "Half-Blood Prince" as a personal nickname combining his magical heritage and family background. The "Half-Blood" part refers to his blood status as a wizard born to a witch mother, Eileen Prince, and a Muggle father, Tobias Snape, making him a half-blood wizard. "Prince" is the maiden name of his mother, which he uses as a tribute to her family. Snape's choice of the name also represents his desire to embrace his magical heritage proudly while distancing himself from his Muggle father. The nickname reflects his complex identity and difficult childhood, as well as his potency in magic, as he used this name in his potions book during his Hogwarts years.