An Etymological Dictionary of Astronomy and Astrophysics

A general tendency, course, or direction.

Etymology (EN): From M.E. trenden “to roll about, turn, revolve,” from O.E. trendan, (cf. O.E. trinde “round lump, ball,” O.Fris. trind, M.L.G. trint “round,” M.L.G. trent “ring, boundary,” Du. trent “circumference,” Dan. trind “round”).

Etymology (PE): Ravâl, from row present stem of raftan “to go, walk, proceed” (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- “to go; to attack”) + suffix -âl, → -al.