Sidney Luxton Loney

1. THE word Trigonometry is derived from two Greek words, one signifying a triangle and the other signifying I measure, and originally denoted the science in which the relations subsisting between the sides and the angles of a triangle were investigated; the science was called plane trigonometry, or spherical trigonometry, according as the triangle was formed on a plane surface or on a spherical surface.

— from Plane trigonometry, 1856