Lashon Hakodesh (Hebrew: לָשׁוֹן הַקֹּדֶשׁ; lit. "the tongue of holiness" or "the Holy Tongue").

Lashon Hakodesh (Hebrew: לָשׁוֹן הַקֹּדֶשׁ; lit. "the tongue of holiness" or "the Holy Tongue"), also spelled L'shon Hakodesh or Leshon Hakodesh (Hebrew: לְשׁוֹן הַקֹּדֶשׁ‎), is a Jewish term and appellation attributed to the Hebrew language, or sometimes to a mix of Hebrew and Aramaic, in which its religious texts and prayers were written, and served, during the Medieval Hebrew era, for religious purposes, liturgy and Halakha – in contrary to the secular tongue, which served for the routine daily needs, such as the Yiddish language.

https://en.wikipedia.org/wiki/Lashon_Hakodesh