E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
It is said that Lundy Foot, a Dublin tobacconist, set up his carriage, and asked Emmett to furnish him with a motto. The words of the motto chosen were Quid rides. The witticism is, however, attributed to H. Callender also, who, we are assured, supplied it to one Brandon, a London tobacconist.
Rides, in English, one syllable. In Latin (why do you laugh?) it is a word of two syllables.