Why hatters were considered mad

Dear Matthew Alice: Where did the expression “mad as a hatter” come from? What’s a hatter, and why is a hatter so pissed off? — Don’t Get It, San Diego

You sure don’t, Don’t. The hatter isn’t steamed, he’s nuts. Loony. Daffy. Dotty. Crazed. Bughouse. A.k.a. “mad,” as in madhouse, madman, mad dog, mad(ding) crowd. And a hatter is a guy who makes hats. (Duh...) That doesn’t sound like much of a high-risk profession, but back in the Victorian era, hat makers used pure mercury to put a glossy finish on top hats. Hatters went bonkers from huffing toxic mercury fumes and absorbing it through their skin every day.