ציטירנדיקער פּירוש אויף ישעיהו 33:19

a people of a strange tongue With another language, which is not the Holy Tongue. A similar expression is (Isa. 33:19): “A people of a strange tongue you shall not see, a people of speech too obscure, etc.” The “nun” and the “lammed” are interchangeable, like נִשְׁכָּה, chamber, which is [equivalent to] לִשְׁכָּה, in the Book of Ezra (Neh. 13:7).