Ikezuki (池月)is the name of a white horse that belonged to Shōgun Yoritomo and also makes an appearance in the Tale of Heike, being ridden by Sasaki Takatsuna, as well as other appearances throughout the Genpei War.
Ikezuki's father taught him to swim in the strong currents of the Yoshino River.
One day, his mother fell into a marshy pond and died.
He stood at the bank of the pond and caught a glimpse of her (failing to realize that it was actually his own reflection).
Villagers saw the image of him jumping over and over again into the pond (ike 池) with a beautiful moon (tsuki/zuki 月) behind him and therefore named him "Ikezuki".