In the first years of WWII, the British Army method of shipping gasoline involved thin tinned steel cans cased in wooden boxes. During transport the crates got loaded up with sand and fine gravel and the thin cans developed leaks. They were derisively called "flimsies".
As the war in North Africa raced back and forth along the coast time and again, the British began to capture large numbers of the German 20 liter fuel cans. So superior were the German fuel cans the Brits began to copy them. The British referred to them with reference to their German origins, Jerry cans, as the Germans were referred to as Jerries.
When the SAS transport morphed to overland insertion rather than parachute drops (the first few missions of which were inserted hundreds of miles behind enemy lines by the Long Range Desert Group in their highly modified 1-ton Chevy 2WD pickups), they adopted newly supplied US Jeeps festooned with jerrycans laid flat on the hood and in other orientations all over the vehicles.