It was the goat that gave it away.
Some young wizards-to-be discover their destinies through an engraved invitation. But for Sparrowhawk, unscrubbed and unbiddable goat herder on the island of Gont, an overheard word in the true, magical language was enough to get him started. Not just one stubborn goat but the whole herd was brought to heel with a single word. Clearly the lad had potential.