The Collaborative International Dictionary of English v.0.48:

Merry-andrew \Mer"ry-an"drew\ (m[e^]r"r[y^]-[a^]n"dr[udd]), n.
   One whose business is to make sport for others; a buffoon; a
   zany; especially, one who attends a mountebank or quack
   doctor.
   [1913 Webster]

   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.
         [1913 Webster]