As merry as a grig

[etymology uncertain], a saying supposed by some to be a corruption of "As merry as a Greek; " by others, to be an allusion to the cricket.

See also: Grig

References in classic literature ?
But though he was as happy as the day was long, and as merry as a grig, the King's daughter fretted all day, thinking of the indignity that had been done her in making her marry Martin, the poor widow's son, instead of a rich young Prince from a foreign country.
The archer, however, who had drunk more than any man in the room, was as merry as a grig, and having kissed the matron and chased the maid up the ladder once more, he went out to the brook, and came back with the water dripping from his face and hair.
The learned gentleman who does the withering business and who blights all opponents with his gloomy sarcasm is as merry as a grig at a French watering-place.