According to historical records, after the establishment of Hogwarts, Dean Slytherin disagreed with the other three deans because of his refusal to admit Muggle students, and the last one left the school. Thousands of years later, everyone in the wizarding world knows that the Slytherin descendant is "Voldemort", but they don't know that the Slytherins from a thousand years ago are not only the descendants of the great Salazar Slytherin.
Intent: Long live Hogwarts! Long live Slytherin!