"The master was an old Turtle--we used to call him Tortoise--' Why did you call him Tortoise, if he wasn't one?' Alice asked. We called him Tortoise because he taught us,' said the Mock Turtle angrily; 'really you are very dull!' You ought to be ashamed of yourself for asking such a simple question,' added the Gryphon; and then they both sat silent and looked at poor Alice, who felt ready to sink into the earth."

Source: Lewis Carroll (2016). “Alice's Adventures in Wonderland”, p.57