The first time Anton encountered the Repelling Charm, he hadn't even started school yet. After trading Potion Ingredients from Fiennes's collection to Professor Snape for Gold Galleons, he'd gone to Diagon Alley and bought his own textbooks. (Chapter 19)
Standard Book of Spells, Grade 1 was a Charms Class textbook that first-year Young Wizards had to buy when they started school.
It listed a whole host of Charms: the Softening Charm, the Cutting Charm, the Unlocking Charm, the Levitation Charm, the Locking Charm, the Mending Charm, the Repelling Charm, the Wand-Lighting Charm, the Fire-Making Charm...
The Repelling Charm was one of them.
"Back then, I was especially interested in the Levitation Charm. I thought that was a kind of talent..." Anton smiled at everyone in the valley. "We should learn to recognize these talents. Magic is the power of the mind. We seek out the power within our minds and find the magic best suited to us."
"Of course, that's the subject of our next lesson: Innate Talent Magic. Let's return to the most basic spell, the Repelling Charm."
"Many sensitive children and wizards who have been hurt inside deeply wish for everything around them to go away. That wish is a kind of power."
Anton stepped forward, crouching slightly. He extended one hand and held his Wand in the other, elbow bent, striking the standard casting stance.
Then he slowly swept his Wand, stepping forward with his back foot and carefully demonstrating the Repelling Charm's casting motion.
"Full-Force Repulsion! (Flipendo!)"
A spellbeam like a bolt of plasma, over three feet (one meter) thick, flared to life and shot from the tip of his Wand at tremendous speed, striking a boulder some distance away.
Whoosh~
The boulder flew off at incredible speed, as if fitted with a rocket booster, hurtling