Webster's 1913 Dictionary

Definition: \Mer"ry-an"drew\, n.
One whose business is to make sport for others; a buffoon; a
zany; especially, one who attends a mountebank or quack
doctor.

Note: This term is said to have originated from one Andrew
Borde, an English physician of the 16th century, who
gained patients by facetious speeches to the multitude

God Rest You Merry, Gentlemen!