(Latin, fidis or fides). He was first fiddle. Chief man, the most distinguished of the company.
The Scotch fiddle or Caledonian Cremona. The itch. As fiddlers scratch with a bow the strings of a fiddle, so persons suffering from skin-irritation keep scratching the part irritated.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894