Ursula K. Le Guin coined the word "ansible" in her 1966 novel Rocannon's World. The word was a contraction of "answerable", as the device would allow its users to receive answers to their messages in a reasonable amount of time, even over interstellar distances.
The plot device of the ansible was the basis for creating a specific kind of interstellar civilization – one where communications between far-flung stars are instantaneous, but humans can only travel at relativistic speeds. Under these conditions, a full-fledged galactic empire is not possible, but there is a looser interstellar organization, in which several of Le Guin's protagonists are involved.
Photo by Marian Wood Kolisch