But it is pronounced “Willis” … at least according to my long-dead grandpa who owned at least two; including one that still had all its original Army markings, radio brackets, etc.FWIW, it's Willy's, i.e Willys-Overland Motors,
not Willis.
During WW2 Willys and Ford were the main producers of the Jeep.
Willy's produced the MA's and MB's, Ford produced the GP's and GPW's.
The Bantam Car Co. was the inventor and original manufacturer of the WW2 era 1/4 ton jeep (Bantam BRC-40) but couldn't keep up with production demands.