E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Rebus (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 quæ geruntur (on the current events). That these squibs might not be accounted libellous, they employed hieroglyphics either wholly or in part.