The Celtic Myth Podshow has a brief introduction to the life of Robert Kirk, an Irish clergyman most famous for his 1691 book The Secret Commonwealth of Elves, Fauns, and Fairies.
Kirk’s account of the secret commonwealth combines the banal with the surreal. They live in houses underground that are large and fair, lit with lamps and fires but without fuel to sustain them. They may abduct mortal women to nurse their children. Their clothing and speech is that of the country they live in. Their life span is longer than ours, but eventually they die. They have rulers and laws but no discernible religion. Moreover, unlike us, they do not have a dense, material form but have, in Kirk’s words,
“Bodies of congealed Air”.
Every Quarter they travel to fresh lodgings, a reference perhaps to the elemental tides of the seasons.