It started in the early 1970's.
At the Ames Research Center (NASA's research center) there was a program that was in development that aimed at created a substance that could help the astronauts deal with the g forces they encountered during take off.
The researchers believed that the best way to deal with g force was to develop some sort of material that could conform to the body of the astronaut and hold the conformity.
But the problem they ran into was that the foam mold's they were using to keep the astronauts in place were not working if the astronaut came out of the mold only slightly.
They needed to develop a foam that would mold as pressure and weight was applied to it so that any movement by the astronaut would be supported.
They also needed that foam to return to its original form once pressure and weight was released from the spot.
This new foam they created was visco-elastic foam which could conform to the shape of the astronauts body and allow for an even distribution of the weight and pressure of the astronauts body over the entire surface of the foam (instead of concentrating in one area).
Once NASA perfected the foam it was only a matte of time before it was fashioned into a form fit for mass consumption.
For years after the NASA creation of the foam only they used it.
But then they allowed it to be used in hospitals and other medical facilities because of it's properties.
Now over 30 years later it's available to everyone!