There are at least two towns called Slapout in the United States, and it looks like they both got their name in pretty much the same way.
During the depression, highway three was built across Oklahoma. Where it passed his land, a fellow named Tom Lemons moved a chicken coop over to the highway and started a store. His sister worked in the store, and whenever the someone would come in looking for something that they didn’t have she would reply that they were “slap out” of the product. Despite Tom’s protestations, the name stuck, and the town became known as Slapout, Oklahoma.
Some other time, maybe about the same time but data is sketchy, there was a store called the Boys Store in a the community of Holtville, Alabama. If you went into the Boys Store and asked for something they were out of you would be told that they were “slap out of it.” Here too, the name stuck.
Two towns in the US, both with the same name, and the same story about how they got their name. Fascinating.