An Etymological Dictionary of Astronomy and Astrophysics

An instrument for the measurement of angles, used in surveying. It consists essentially of a telescope moving along a circular scale graduated in degrees.

See also: The first occurrence of the word theodolite is found in the surveying textbook A geometric practice named Pantometria (1571) by Leonard Digges, which was published posthumously by his son, Thomas Digges. The etymology of the word is unknown. The first part of the New Latin theo-delitus might stem from the Gk. theaomai “to behold, view attentively, contemplate,” but the second part is more puzzling and is often attributed to an un-scholarly variation of delos “evident, clear.”