Lettic

a.
  1. Of or pertaining to the Letts; Lettish.
  2. Of or pertaining to a branch of the Slavic family, subdivided into Lettish, Lithuanian, and Old Prussian.
  3. The language of the Letts; Lettish.
  4. The language of the Lettic race, including Lettish, Lithuanian, and Old Prussian.