Is it farther or further?
late 14c., "taking words in their natural meaning" (originally in reference to Scripture and opposed to mystical or allegorical), from Old French literal and directly from Late Latin literalis/litteralis "of or belonging to letters or writing," from Latin litera/littera "letter, alphabetic sign; literature, books" (see letter (n.1)). Meaning "of or pertaining to alphabetic letters" is from late 15c. Sense of "verbally exact" is attested from 1590s, as is application to the primary sense of a word or passage. Literal-minded is attested from 1791.