The shachihoko is a mythical beast in Japanese folklore with the head of a tiger and the body of a carp. The shachihoko is most famous for appearing on the ends of ridgepoles on the roofs of Japanese castles. This was because the shachihoko was viewed as bringing good luck, such as causing rain to fall or preventing the wooden castles from catching fire.
The word "shachihoko" is usually written with the kanji character "鯱," which is more commonly used to mean "killer whale," in which case it is pronounced as just "shachi" (the Japanese word for killer whale). This is a cause of some confusion, even among Japanese people, leading people to believe either that the roof ornaments are killer whales (which they are not), or that the name for them is "shachi" rather than "shachihoko."
Alternative ways of writing "shachihoko" in Japanese which are more clear include "鯱鉾" (which is more obviously pronounced "shachihoko") and "魚虎" (literally, "fish tiger").
For some reason, the word "shachihoko" is invariably translated into English on Japanese signs and plaques as "grampus," an obscure and archaic English word which almost no English native speaker will understand. This is why the professional soccer team in the city of Nagoya, which is famous for Nagoya Castle, is known as the Nagoya Grampus.