The midget radio was so-called for it's diminutive size. RCA, Standard Electric, Arvin and Emerson all had early models. Manufacturers called them midgets because they were under two feet tall, and only weighed 25 lbs. More here.
Air-King produced the first plastic chassis radio with a model. The idea here was not electrical. It was pure cost-cutting. A plastic chassis didn't need glued, sanded or finished as wood certainly did.
the earliest models in the 1930s had wooden chassis like miniature versions of the beasts that they replaced. Later 1950s versions were often art deco and made of Bakelite plastic.
Not all radios were hopelessly large because of the technology at the time. In a 1941 issue of Popular Science they showed off a hand-held radio. It only required that you pound a nail into the earth for a ground and mount 40 feet of antenna wire between trees. As ridiculous as that sounds, midget radio became increasingly important.
A 1959 Billboard article called them a "pocket sized threat. They went on to say that
"Teenagers have been noted walking along the route to school or perhaps the after-school soda hangout, with an earplug in one ear. This is in reality a midget earphone attached to a midget transistor radio. In this way the favorite Top-40 jockey is never any further away then the then the switch on the radio..."Does that sound to you like an Ipod?