Penitenziagite ("Do Penance") is a rallying cry derived from the Latin "Poenitentiam agite," meaning the same. It has been also interpreted as a paraphrase of the Greek "πένητες διάγετε" attributed to Christ ("penites diagete"), meaning "live life as a pauper".
The phrase was used by the Dulcinian movement founded by Gerard Segarelli (1240–1300) in the 13th century, a movement named after the disciple Fra Dolcino.
The phrase is used in the novel The Name of the Rose by Umberto Eco and in the Jean-Jacques Annaud movie of same name.
A sample of Ron Perlman saying the word appears in the song Endemoniada, the first track on the album The Nephilim, by Fields of the Nephilim.
References
Penitenziagite Wikipedia(Text) CC BY-SA