Kievan period and feudal breakup[edit]
The 14th-century Novgorodian children were literate enough to send each other birch-bark letters written in the Old Novgorod dialect.
Up to the 14th century, ancestors of the modern Russians (who likewise called themselves ruskiye[citation needed]) spoke dialects of the Old East Slavic language, related to the dialects of other East Slavs. This spoken tongue and the literary Old Church Slavonic language operated throughout Kievan Rus. The earliest written record of the language, an amphora found at Gnezdovo, may date from the mid-10th century. (Until the 15th century, Gnezdovo was a part of the independent Principality of Smolensk.)
For the debate concerning derivation of the words Rus and Russia, see Etymology of Rus and derivatives and Rus' (people). For the general history of the language and Old East Slavic literature, see Old East Slavic language.
During the pre-Kievan period, the main sources of borrowings were Germanic languages, particularly Gothic and Old Norse. In the Kievan period, however, loanwords and calques entered the vernacular primarily from Old Church Slavonic and from Byzantine Greek: