Cushing's disease was originally diagnosed in a human in 1932 by Dr. Harvey Cushing.
I actually prefer the medical term for the disorder: hyperadrenocorticism. It's a mouthful, but it's more descriptive of the condition.
'Hyper' means too much, 'adreno' refers to the adrenal glands, and 'corticism' refers to a syndrome involving the hormone cortisol. Hyperadrenocorticism, loosely translated, means too much cortisol released by the adrenal glands.
Cushing's disease is rarely seen in kitties. The condition is most often seen in dogs.