(Latin, with things). A hieroglyphic riddle, “non
verbis sed rebus.” The origin of the word and custom is this: The
basochiens of Paris, during the carnival, used to satirise the current
follies of the day in squibs called De rebus quae geruntur (on
the current events). That these squibs might not be accounted
libellous, they employed hieroglyphics either wholly or in part.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894