He has let a brewer's fart, grains and all; said of one who has bewrayed his breeches.
Piss and fart. Sound at heart. Mingere cum bumbis, Res saluberrima est lumbis.
I dare not trust my a-se with a fart: said by a person troubled with a looseness.
A footboy; so called from such servants commonly following close behind their master or mistress. ...
Dictionary of The Vulgar Tongue by Francis Grose
A valet or footman from his walking behind his master or mistress. ...