Before the unification of Nepal, the Kathmandu Valley was known as ''Nepal''. The precise origin of the term ''Nepāl'' is uncertain. ''Nepal'' appears in ancient Indian literary texts dated as far back as the fourth century BC. However, an absolute chronology can not be established, as even the oldest texts may contain anonymous contributions dating as late as the early modern period. Academic attempts to provide a plausible theory are hindered by the lack of a complete picture of history and insufficient understanding of linguistics or relevant Indo-European and Tibeto-Burman languages.