The term "Baltic" stems from the name of the Baltic Sea – a hydronym dating back to the 3rd century B.C. (Erastothenes mentioned in Ancient Greek) and earlier. Although there are several theories about its origin, most ultimately trace it to the Indo-European root "*bhel" meaning 'white, fair'. This meaning is retained in modern Baltic languages, where in Lithuanian and in Latvian mean 'white'. However, the modern names of the region and the sea that originate from this root, were not used in either of the two languages prior to the 19th century.