What about the Hillman Minx? 

I don't see "Minx" as an adjective. It's a noun. Using it to describe a cat seems redundant ("she's a minx" means something like "she's catty," I thought  "a minx" is some sort of fighting feline). 

The Hillman Minx car, in the 1950's, was a very small automobile (smaller than a Volkswagen beetle) its name probably meant to suggest that it was sprightly and energetic despite its tiny size and low power (I only know of it that our family owned two of them  a grey one with yellow ear-flaps, and later a red one  the Minx could not go fast, so its driver had to outwit other cars rather than overtaking them...). 

Perhaps the minx relies more on wit and slyness than on physical strength?