E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
as the sign of a grocer, is the crest of Sir Thomas Gresham, the merchant grocer. The Royal Gresham Exchange used to be profusely decorated with grasshoppers, and the brass one on the eastern part of the present edifice is the one which escaped the fires of 1666 and 1838.
There is a tale that Sir Thomas was a foundling, and that a woman, attracted by the chirping of a grasshopper, discovered the outcast and brought him up. Except as a tale, this solution of the combination is worthless. Gres=grass (Anglo-Saxon, grs), and no doubt grasshopper is an heraldic rebus on the name. Puns and rebuses were at one time common enough in heraldry, and often very far-fetched.