Rather a debatable fairy. The Oxford Dictionary gives the word as meaning a dwarf or something small, a baby eel, a cricket. There is, however, a fairly widespread idea that the proverbial expression 'As merry as a grig' relates to fairies, and in Somerset 'griggling apples' are the small apples left on the trees for the fairies. Ruth Tongue heard a story, 'The Grig's Red Cap', from a groom at Stanmore, Harry White, in 1936, and an earlier version of it from the Welsh Marches in 1912. According to both of these, the grigs were small, merry fairies dressed in green, with red stocking caps, a costume which could indeed apply to fairies in a good many places, as, for example, the wee folk in Ireland. It is possible that the idea of smallness and the expression 'merry as a grig' built up a kind of pseudo-fairy about the word 'grig'.

[Motifs: F236.1.6; F236.3.2]