A cholagogue is a medicinal agent which promotes the discharge of bile

Bile

Bile or gall is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the process of digestion of lipids in the small intestine. In many species, bile is stored in the gallbladder and upon eating is discharged into the duodenum...

 from the system, purging it downward.

In Patrick O'Brian's book "The Post Captain," which is set in the Napoleonic era, Stephen Maturin, one of the book's main characters (who is also a physician, naturalist and spy) sits in the snug of the Rose and Crown in Deal and drinks a "good" tea described as an "unrivalled cholagogue".