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.
Erlking
It has been suggested, that the term may derive not from "elf-king" but from the name of "Herla", a figure in medieval English folklore, adapted as "Herlequin", "Hellequin" in medieval French, in origin the leader of the Wild Hunt, in French known as "maisnie Hellequin" "household of Hellequin" (and as such ultimately identical with Woden), but recast as a generic "devil" in the course of the Middle Ages (and incidentally, in the 16th century also the origin of the Harlequin character). Sometimes also associated is the character of "Herrequin", a ninth-century count of Boulogne of proverbial wickedness.