“This is your copy of
Advanced Potion-Making, is it, Potter?�
“Yes,� said Harry, still breathing hard.
“You’re quite sure of that, are you, Potter?�
“Yes,� said Harry, with a touch more defiance.
“This is the copy of
Advanced Potion-Making that you purchased from Flourish and Blotts?�
“Yes,� said Harry firmly.
“Then why,� asked Snape, “does it have the name ‘Roonil Wazlib� written inside the front cover?�
Harry’s heart missed a beat. “That’s my nickname,â€� he said.”
―
J.K. Rowling,
Harry Potter and the Half-Blood Prince