The Rite.
Bernard Grobbin was a very successful cattleman on the Sto plains. Bernard's first son was the heir to his cattle ranch, and the following six sons grew up to be fine ranch hands. The next son, Ernie grew up to work in and eventually run his own tannery. Ernie also had many sons, the eighth of which he named Barney. Shortly after his son's birth, Ernie had an unexpected visitor: a wizard called Crumb. Crumb looked at Ernie, and said "Do you know why I am here?"
Ernie's expression was blank, "I can't say I do Mr. Crumb."
Crumb sighed: sometimes you met people who didn't know how things worked. "You are the eighth son of Bernard Grobbin are you not?" He eyed Ernie, who nodded blankly, "and your newest child is your eighth son correct?" Ernie nodded again, "that happens to make him a wizard. I am your 3rd cousin, and that makes me his closest wizardly relative, so it is my duty to guide him."
"So what should I do?" Ernie asked.
"As it happens, your village elders have recently contacted the Unseen University to request a village wizard: someone to help out with magical matters and to help protect the place, so I shall be moving in. I will help teach and guide the boy, and when he is old enough we will attempt to secure the chance for him to be taught by my colleagues in the University. And before you ask, it will probably be his eighth birthday." Crumb responded.
"Oh, okay." Ernie mumbled.
And so the wizard Crumb settled into village life, becoming a sort of doctor slash magical protector. Young Barney became Crumb's apprentice and to his family's surprise started to exhibit strong magical potential.
Crumb spent the next few years carefully arranging things so that the boy could enroll in the Disc's premier magical learning establishment on his eighth birthday.