E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
So called from Piccadilla Hall, the chief depôt of a certain sort of lace, much in vogue during the reign of Queen Elizabeth. The lace was called piccadilly lace, from its little spear-points (a diminutive of pica, a pike or spear). In the reign of James I. the high ruff was called a piccadilly, though divested of its lace edging. Barnaby Rice, speaking of the piccadillies, saysHe that some forty years sithen should have asked after a piccadilly, I wonder who would have understood him, and would have told him whether it was fish or flesh (1614). Another derivation is given in the Glossographia (1681). Piccadilly, we are there told, was named from Higgins famous ordinary near St. Jamess, called Higginss Pickadilly, because he made his money by selling piccadillies (p. 495). (See also Hone: Everyday Book, vol. ii. p. 381.)
Where Sackville Street now stands was Piccadilla Hall, where piccadillies or turnovers were sold, which gave name to Piccadilly.Pennant.