Silencers were invented by Hiram Maxim, the son of a U.S. inventor.
His father, Hiram Stevens Maxim, invented the first machine gun that was fully automatic. Maxim was a mechanical engineer and MIT grad.
At the time, the silencer he created was sold for just above $3.00 per unit! It was pretty effective as well, not much different than the modern silencers of today.
Although silencer has been used quite often, especially as a result of many modern movies, the correct term is (or was) actually suppressor.