Mad as a hatter

When Lewis Carroll wrote Alice in Wonderland in 1865, this expression was already well known but he did immortalise it with his famous personification of The Mad Hatter. Hat makers in the early 19th century used a solution of nitrate of mercury to soften and smooth the felt from which hats were made. Over-exposure to the fumes would often lead to mercury poisoning, which is also known as mad hatter syndrome or mad hatter disease. The symptoms were erratic, aggressive behaviour together with trembling and shaking. This gave rise to the expression hatter’s shakes which has more or less died out. In the early 19th century, the favoured expression was angry as a hatter but this was eventually replaced by mad as a hatter after the publication of the very popular Alice in Wonderland.