During the 13th century the Duchy of Lithuania was bordered by Slavic lands. The Slavs did not create the name; they used the existing Lithuanian ethnonym. The Lithuanian diphthong -ie- has, in Slavic languages, shifted to the vowel -i- (и), and the short -u- became (reduced) -ŭ- (ъ) which, being unstressed, later disappeared from the Eastern Slavic, hence Litva. This is evidence that the Slavs borrowed this ethnonym from Lithuanians a long time ago.
During the next century, Lithuania's name was recorded in other languages, including German and Polish. In early German chronicles Lithuania's name was spelled as Lettowen. In this form the German letter -e- is used to denote the Lithuanian diphthong -ie-, while -owen denotes the Lithuanian hydronymic suffix -uva (-ava). The traditional Lithuanian root -liet- is encountered in various German usages of the era, such as Lettowen, and in Latin as Lethovia, Lettovia, Lettavia, etc.
In Rus' chronicles Lithuania's name was written as Литъва, alongside a shortened version, Литва (Litva), where -i- (и) was already used instead of the diphthong -ie. All of these names clearly originated from *Lētuvā > Lietuva, forms used by Lithuanians to identify their lands. The current form of the name Lietuva is thought to have been used by Lithuanians since the 12th or 13th century, but there are no written sources of that time, as the oldest existing manuscript in the Lithuanian language is dated back to the 16th century. Despite ample historic and linguistic evidence with regard to the name's usage in different languages, there is a certain degree of debate about the etymology of the name.