A brief bit of totally obscure history that I am one of the few living persons who knows.
My family business, established in Pontiac, Michigan in 1905, is the original manufacturer of the "Welch" plug. The Welch brothers had a motor car company at the turn of the century that was later bought by General Motors - the Welch Motor Car company. They would run the cars around Pontiac to "break them in."
At that time core holes in the engine blocks were fitted with pipe plugs. During one of these run-ins a pipe plug backed out. In order to get back on the road one of the brothers drove a quarter or half dollar into the hole. From this they developed the Welch plug, some with the help of my Great Grandfather Martin Hubbard. They then patented the plug and the M.D. Hubbard Spring Company become the sole manufacturer of the Welch plug for the life of the patent. To this day we have the largest range of sizes available anywhere.
So the Welch plug in origin is an American innovation and name.