from Wiktionary, Creative Commons Attribution/Share-Alike License.
superlativeform of squatty: most squatty.
Sorry, no etymologies found.
Note that I am easily the happiest person in the photo, and definitely the squattiest.
On one of these points a large, broad-nosed hippo was standing, looking as shapeless as if it had been roughly modelled in mud, and set upon four legs of the shortest and squattiest kind.