From Proto-Balto-Slavic *tenˀwas, from an old Proto-Indo-European u-stem noun *ténh₂us to which secondary adjectival endings were added (*tenh₂-u-os), from Proto-Indo-European *tenh₂- (“to stretch, to pull, to strain”) (whence also tīt (“to wind, to coil, to wrap”), q.v.). Cognates include Lithuanian tévas (“slender, thin, delicate”), Proto-Slavic *tьnъ (Old Church Slavonic тьнъкъ (tĭnŭkŭ), Russian то́нкий (tónkij), Ukrainian то́нкий (tónkyj, “thin, delicate”), Bulgarian тъ́нък (tǎ́nǎk, “slender, thin, delicate, light”), Czech tenký (“thin, delicate”), Polish cienki (“thin, fluid”), Upper Sorbian čeńki (“thin, weak”)), Old High German thunni, dunni (“slender, thin”), German dünn, English thin, Sanskrit तनु (tanú, “slender, thin, small, weak”), Latin tenuis (“slender, thin, narrow, delicate, simple”), Ossetian тӕн (tæn, “slender, thin”).