The term originates in Simulacra and Simulation (1981) by Jean Baudrillard. In Simulacra and Simulation Baudrillard deals with the relations between society, symbols and reality. See simulacrum? and simulation?.
The 1946 short story On Exactitude in Science by Jorge Luis Borges depicts a civilisation that has advanced thus far in cartography that only a 1:1 map will suffice. When the map is finally drawn up, the result is an exact copy of reality that covers the entirety of the kingdom. As time passes and younger generations lose interest in cartography, the map becomes cumbersome. Left to decay for years only fragments remain, now inhabited by animals and beggars.1 Inspired by this story, Baudrillard uses it on the first page of Simulacra and Simulation. The map, being an exact copy of reality, is a simulation. The fragments that are copies of something that once was, are simulacra.2 Hyperreality is the state in which it is impossible to distinguish from each other the reality, the simulation and the simulacrum. Baudrillard compares our current reality with the map of the territory that no longer exists: "generation by models of a real without origin or reality".3
2 simulacra definition. Retrieved January 3, 2016, from http://it.stlawu.edu/~global/glossary/simulacra.def.html
3 Baudrillard, J. (1994). Simulacra and simulation. Ann Arbor: The University of Michigan Press. p. 1