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.
Erebuni Fortress
The Circassian historian Amjad Jaimoukha gives an alternative etymology, however: "eri" (referring to the Èrs, the people living in the area) + "buni". "Buni" comes from the Nakh root which spawned the Chechen word "bun" meaning shelter or cabin; the root however simply means lair or shelter. With its Indo-European roots "bun" initially derives from the Armenian word "buyn" (բույն) for "nest" or "lair". From Proto-Indo-European *bʰeuH-no-, from *bʰeuH- (“to be; to grow”). Cognates include Sanskrit भुवन (bhúvana, "world"), Albanian bun ("shepherd's hut") and Middle Persian بن bun ("bottom"). It may have spawned the word "van" in Armenian (a language with a strong Urartian substratum), albeit possibly through different roots (Urartian "biani" rather than Èr "buni") which similarly means shelter. "Van" as a root is also present in numerous other placenames in historical Armenia, including the city Van, Lake Sevan, and Nakhichevan, so it is probable that the "van" in "Yerevan" is another direct translation of the root. Jaimoukha states furthermore that the name of the Èr also serves as the root for the Arax valley (the Erashki gorge) and for the Medieval Georgian name used in the "Georgian Chronicles" for Lake Sevan- "Lake Ereta".