// It means "Not On Normal Courtyard Exercise" //
No it doesn't.
From Wikipedia...
//The Oxford English Dictionary, while describing the word's etymology as "Origin unknown", states that it is "perhaps related to" nance and cites a quotation which claims the word was derived from nancy-boy (a derogatory term referring to effeminate or homosexual males). It also suggests that it may derive from the nonse, Lincolnshire dialect for "good-for-nothing fellow".[4]
Linguist Jonathon Green suggests the word derives from nonsense. He quotes a reference from 1970 citing "nonces" as being short for "nonsenses" and an additional citation from 1999//