Ex nihilo

Another Latin phrase seen in English is nihil obstat 'nothing hinders'. It's the sort of thing one used to see on the copyright side of the title page in books which had been approved for printing by a Catholic bishop. Usually accompanied by the imprimatur 'it may be published'. In the Middle Ages, there was a tendency to spell nihil as nichil, pronounced a bit like our nickel.

Ceci n'est pas un seing.