E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The difficulty of tracing the fons et orgo of slang words is extremely great, as there is no law to guide one. Generally, a perversion and a pun may be looked for, as Monseigneur = toe (q.v.), Monpensier = ventre (i.e. monpanse, my paunch or belly), etc. (See SANDIS, SQUASH, and numerous other examples in this dictionary. For rhyming slang see CHIVY.)