The fabled Irish chieftain O'Donohue is
said to return to the lakes of Killarney on his great white horse every
seventh year on May Day, gliding over the waters to sweet but unearthly
music, a host of fairies preceding him and strewing his path with spring
flowers. Waves created with foam on a windy day are thus known as
O'Donohue's white horses.
According to legend, at least one beautiful young girl believed in
O'Donohue so strongly that she threw herself in the water so that he would
carry her off for his bride.
The term "wild horses" is also used for crested waves, as in Matthew
Arnold's poem The Forsaken Merman:
The wild horses play,
Champ and chafe and toss in the spray.