"Mad as a hatter" is a colloquial English phrase used in conversation to suggest (lightheartedly) that a person is suffering from insanity. The etymology of the phrase is uncertain, with explanations both connected and unconnected to the trade of hat-making. The earliest known appearance of the phrase in print is in an 1829 issue of Blackwood's Edinburgh Magazine, predating the Hatter from Lewis Carroll's Alice's Adventures in Wonderland by several decades.