The pigeon vest was a vest that was created to protect carrier pigeons as they parachuted through the air strapped to the chest of paratroopers during World War II. Once the paratroopers hit the ground behind enemy lines, they would release the pigeons so they could fly off to deliver important messages.
And what does this have to do with brassieres? The pigeon vest was designed and manufactured by the brassiere company, Maidenform. On December 22, 1944, Maidenform agreed to make 28,500 pigeon vests for the U.S. government, switching, as many companies did, from peacetime production to producing necessary supplies for the war. In addition to the pigeon vest, Maidenform also made parachutes.
RTFA. It all makes sense.