Cardan grille

Etymology
Proposed in 1550 by Girolamo Cardano (1501-1576), known in French as Jérôme Cardan.

Noun

 * 1)  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.