E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.
Merry as a Cricket, or as a Lark, or as a Grig.
The French say, “Fou (or Folle) comme le branlegai,” and more commonly “Gai comme un pinson” (a chaffinch). “Branlegai” is a dance, but the word is not in use now.
