Phouka (or Puca)
The Irish form of a European field spirit, the kornböcke,
one of various kinds of animal fairies. The phouka would appear
as a goat, a pig, or, most frequently, as a horse. It would
lure its victims to mount it, then take them for a wild ride and
throw them off. It is possible that the word puca is related to
Puck, another mischievous fairy figure.
Arrowsmith, Nancy, and George Moorse. A Field Guide to the
Little People. New York Wallaby Books, 1977.