New Word: “Carapace”

This is a physical word that was used in an emotional context.  Technically a carapace is:

A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises…

Basically, it’s a shell.  I encountered the word in a marvelous book called The Emperor of All Maladies, which is a history of cancer.  In it, the author describes a cancer patient descending into the hell of chemotherapy, and shutting herself off emotionally from the people around her:

Her melancholy hardened into something impenetrable, a carapace, and she pulled into it instinctually, shutting everything out.

“Pulled into it” is clearly a reference to the shell of a turtle, of which the word seems to most often refer (though, technically it refers to the shell of lots of different things).