Ewwwwww…
… answer a few questions at The Oatmeal (site of previously-featured gems like this) and find out.
As we reach for the disinfectant wipes, we might recall that it was on this date in 1946 that the electric blanket, which had been invented in the form still known today in 1936, was first put on sale by the Simmons Company.
As this 1941 article attests, others were at work on the electric blanket as well… (source)