Source : Webster's Revised Unabridged Dictionary (1913)

Themis \The"mis\, n. [L., fr. Gr. ?, fr. ? that which is laid
   down or established by usage, law, prob. fr. ? to set,
   place.] (Gr. Myth.)
   The goddess of law and order; the patroness of existing
   rights.

Source : WordNet®

Themis
     n : (Greek mythology) the Titaness who was goddess of justice in
         ancient mythology