Aleksandr Solzhenitsyn wrote in his book The Gulag Archipelago about how the Soviets avoided the term prisoners:
The population of Ryazan [the location of a concentration camp set up in a former nunnery (Kazansky)] was very sympathetic toward the deprivees, as they were called. (Officially they were called not prisoners but “persons deprived of freedom.”)
The Gulag Archipelago, Volume 2, p 20