Gulag is the russian word for prison

According to wikipedia, no, it comes from the abbreviation of “Main Directorate of Correctional Labour Camps”, in Russian: Гла́вное Управле́ние исправи́тельно-трудовы́х ЛАГере́й (ГУЛАГ).

If you would consult the chart:

“system of places for deprivation of liberty”

You will find “Correctional Labor Camp” under the O.G.P.U (as wikipedia also says). Of course, libs can’t tell the difference between CLC under the O.G.P.U and Colonies under the PC of Justice and will call both gulag.