The general idea of shock troops has been around pretty much forever. When you have a defending force that's dug in and an attacking force, just throwing your standard line infantry against the defenses is rarely effective. So, you need heavier, better trained soldiers that can crack the defensive lines before sending a full infantry assault. This role was preformed by Viking berserkers, heavy cavalry units, and mercenary German Doppelsöldner. In a way, since the very beginning of warfare there have been troops that are better trained by the rest and are sent into battle first, so while they weren't called "shock troops" the concept is fundamental to military theory.

The actual term "shock troops" came about during WWI. After the stalemate of trench warfare, the Germans developed new strategies for assault tactics. Their first dedicated assault battalion was formed in the spring of 1915. These soldiers developed into German units of Stroßtruppen, a word that literally means "shock/impact/push/thrust troops". This was the first major dedicated unit of assault troops and they preformed very well during the war, to the degree that the loose translation of shock troops took on the meaning of encompassing all similar assault troops. After WWI, those assault tactics were expanded on and instead of using large groups of untrained men, armies were reorganized into small, much better trained and equipped units. So shock troops is not used as a term very often anymore because the original concept has become a bit of a standard in modern military theory.