 The name may have meant "dark" and can be compared to other cognates such as Russian темно (Proto-Slavic *"tĭmĭnŭ"), Lithuanian "tamsi" "dark", Latvian "tumsa" "darkness", Sanskrit "tamas" and Welsh "tywyll" "darkness" (Proto-Celtic *"temeslos") and Middle Irish "teimen" "dark grey".The origin is shared by many other river names in Britain, such as the River Tamar at the border of Devon and Cornwall, several rivers named Tame in the Midlands and North Yorkshire, the Tavy on Dartmoor, the Team of the North East, the Teifi and Teme of Wales, the Teviot in the Scottish Borders and a Thames tributary the Thame.Kenneth H. Jackson has proposed that the name of the Thames is not Indo-European (and of unknown meaning), while Peter Kitson suggested that it is Indo-European but originated before the Celts and has a name indicating "muddiness" from a root "*tā-", 'melt'.