The original fenya consisted of broken Russian words borrowed from Greek and other foreign languages.
Vladimir Dahl in his Explanatory Dictionary of the Live Great Russian language gives the following examples: The vocabulary changed over time, with notable infusion of words of Yiddish origin.
For one, a significant part of the population, not necessarily criminals, survived the Gulag and were released after the death of Joseph Stalin and during the Khrushchev thaw.
[2] Particularly members of the intelligentsia, including writers, poets, and journalists who had survived the Gulag as political prisoners, began to regularly use fenya in their writings after their release.
The dissolution of the Soviet Union and the appearance of "New Russians" introduced new changes into fenya, notably assigning new meanings and accents to common words.