Wikipedia: “The word steganography is of Greek origin, meaning “concealed writing”, from the Greek words steganos (στεγανός), meaning “covered or protected” and graphei (γραφή), meaning “writing”. The first recorded use of the term was made in 1499, by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book dealing with magic.

 

Generally, messages may appear to be something else: images, articles, shopping lists, or some other cover-text, and the all-time classic: the hidden message may be written in invisible ink between the visible lines of a private letter.

 

(To the left: Screenshot from the documentary “Shakespeare: The Hidden Truth”. First Folio, page 37 of the Comedies, The Two Gentlemen of Verona: Act V, scene IV).