(Sir). In the romance La Mort d' Arthure he is called the fool of King Arthur, and was knighted by the king himself.
“I remember at Mile-End Green, when I lay at Clement's Inn, I was then Sir Dagonet in Arthur's show.” —Henry IV., iii. 2. (Justice Shallow).
“Dagonet” is the pen-name of Mr. G. R. Sims.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894