Definition of Lettonian in English:

Lettonian

Pronunciation /lɛˈtəʊnɪən/ /lɪˈtəʊnɪən/

adjective

rare
  • Of or relating to the Lettonians; Lettish, Latvian.

Origin

Early 18th century (in an earlier sense). From †Lettonia, a former name of the country of Latvia + -an, probably after e.g. Lapponian, Livonian. Compare French †lettonien, and also French letton.