The long names phenomenon is an artifact of modern times. There were two reasons; 1) a "multiplicity" of government types and 2) the desire of some countries to confuse one type for another.
Until the 18th century, there was basically one type of government; rule under a single ruler, which could be subdivided into monarchies and empires. This was not totally true, because Greece experimented with democracy, and Rome with a republic, but this was true enough until modern times, because Greece and Rome were special cases. I would also consider the United Kingdom of Great Britain and (Northern) Ireland ( a union of several states into a country) a special case.
"Greece and Rome" were rediscovered in Europe during the Renaissance, and their forms of government were debated in the 17th century by scholars of the Enlightenment. It wasn't until the late 18th century that these ideas were once again put into practice after the American and French Revolutions as a democracy in the U.S. and a republic in France.
More forms of government, such as Communism, fascism, and fundamentalism were added in the 20th century. That's where you get the long names, as these newer, totalitarian forms of government tried to take on the trappings of the more respected republics and democracies, with the (Communist) People's Republic of China, or the German Democratic Republic (formerly Communist East Germany), or the Islamic Republic of Iran.