зэк

Etymology
Shortening of, via the initialism з|З-к|К. Заключённый is the adjective "prisoner". Каналоармеец, "member of the canal army", was coined in an analogy with the words красноармеец meaning "member of the Red Army" or трудоармеец (member of a labor army). In 1932, when Anastas Mikoyan visited the construction of the White Sea – Baltic Canal, Lazar Kogan told him "Comrade Mikoyan, how shall we call them? (…) I thought up the word: 'kanaloarmeyets'. What do you think?" Mikoyan approved it."

Noun

 * 1)  convict, inmate