Lewis & Short

tristĭtĭes, ēi [tristis], = tristitia,

  1. I. sadness, mournfulness, sorrow, grief (ante- and postclass.): vultum alligat quae tristities? Pac. ap. Non. 182, 2 (Trag. Rel. v. 59 Rib.): tristitiem, Tac. A. 2, 4, 3: tristitie, Turp. ap. Non. l. l. (Com. Rel. v. 126 Rib.); App. M. 4, p. 155, 13; 9, p. 231, 2; 10, p. 239, 18.
  2. II. Personified, Tristĭtĭes, the name of a maid of Psyche, App. M. 6, p. 176, 36.