Fairy Food in the sense of food eaten by fairies, is, evidently, delicate fare. Fairies of different ethnic groups have developed differing diets and foodways and the research which is no doubt being done on the origins of these does not seem yet to have found the original source from which these evolved.
Katharine Briggs (1976), concentrating on fairies of the British Isles, remarks that according to one authority the fairies of the Highlands and Islands of Scotland borrow oatmeal from human beings and return double measure, but in the form of barley, which seems to be ‘their natural grain’. One food offered to the fairies in Ireland was champ, and it has been suggested that bog-butter may sometimes have been intended for them. Fairies are also said to drink the milk of red deer and goats, and to consume large quantities of weeds. These weeds can be made to look like sumptuous fare, a trick which would be convenient for human cooks but which involves the use of glamour in the original sense of the word (magic, enchantment). A converse, negative, technique enables the fairies to extract the essential goodness from human food, leaving it bereft of nutritional qualities.