The story
Proposed in 1550 by Girolamo Cardano (1501-1576), known in French as Jérôme Cardan.
Etymology from Wiktionary, CC BY-SA 4.0.
Cardan grille
Today it means: A sheet of card or thin metal, etc., used in composing secret messages. The words of the message are written through a number of holes cut arbitrarily in the sheet, and the remaining paper is then filled with irrelevant words to disguise it. Full definition →