Cetus's name refers to a sea monster in greek mythology, although it is often called 'the whale' today.
Cetus is located in the region of the sky that contains other water-related constellations such as Aquarius, Pisces and Eridanus.
It is often now called the Whale, thought it is most strongly associated with Cetus the sea monster, who was slain by Perseus as he saved the princess Andromeda from Poseidon's wrath.