Who among the following used ‘untranslatableness’ in his famous work?

The correct option is S.T Coleridge in Biographia Literaria.

In chapter XIV of his major critical work, Biographia Literaria (1817), Samuel Taylor Coleridge introduces the idea of the "untranslatableness" of words in a good poem. He argues that in truly excellent poetry, the words cannot be translated into other words of the same language or another language without a loss of the original poetic force, meaning, and harmony. Coleridge states that the language of such a poem is so precise and organic that any alteration or substitution of words would damage the unified effect of the work.