A generic name for a quack or charlatan. Katerfelto was a celebrated quack or influenza doctor. He was a tall man, who dressed in a long black gown and square cap. In 1782 he exhibited in London his solar microscope, and created immense excitement by showing the infusoria of [muddy] water. The doctor used to aver that he was the greatest philosopher since the time of Sir Isaac Newton.
And Katerfelto with his hair on end, At his own wonders wondering for his bread.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894