Eureka (word)
The exclamation 'Eureka!' is attributed to the ancient Greek scholar Archimedes. He reportedly proclaimed "Eureka! Eureka!" after he had stepped into a bath and noticed that the water level rose, whereupon he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged. (This relation is "not" what is known as Archimedes' principle—that deals with the "upthrust" experienced by a body immersed in a fluid.) He then realized that the volume of irregular objects could be measured with precision, a previously intractable problem. He is said to have been so eager to share his discovery that he leapt out of his bathtub and ran naked through the streets of Syracuse.
Púca
The origin of the name may have come from the Old Norse term "pook" or "puki", which refers to a "nature spirit". Usage of the term in Ireland, however, may predate the arrival of Norse settlers.
In Germanic languages, such as Frisian or English, this became "pucel", "pook" or "puck". The name of the pooka may also come from the Irish word "poc", meaning a male goat, a form the creature is often said to take.