According to a BBC documentary, the word 'nonce' is supposed to have originated in Wakefield Prison in West Yorkshire, England, also known as 'Monster Mansion' because the very worst of the worst offenders got sent there. >The programme shared the the acronym N.O.N.C.E was marked on the cell card of any prisoner who may have been in danger of violence from other prisoners. It meant staff would not open their doors when other prisoners were out. >The acronym NONCE stands for 'not on normal courtyard exercise', according to the documentary, and apparently was first coined at the jail in Yorkshire. https://www.examinerlive.co.uk/news/tv/word-nonce-comes-origins-hmp-23527206