In my last entry the word theodolite cropped up in the OED’s definition of circumferentor; I got curious about its etymology and looked it up, only to find:
Origin unknown… The name, alike in the Latinized form theodelitus and the vernacular theodelite (subseq. -dolite), originated in England, and is not known in French and German until the 19th c. Its first user, and probable inventor, L. or T. Digges, has left no account of its composition, as to which various futile conjectures, incompatible with its early history and use, have been offered; such is the notion that it arose in some way out of alhidada or its corruption athelida occurring in Bourne’s Treasure for Travailers 1578, which an examination of the works of Digges and Bourne, where both words occur in their proper senses, shows to be absurd. Theodelite has the look of a formation from Greek; can it have been (like many modern names of inventions) an unscholarly formation from θεαομαι [theaomai] ‘I view’ or θεω [theo] ‘behold’ and δηλος [dēl-os] ‘visible, clear, manifest’, with a meaningless termination?
Dammit, if people are going to invent words, the least they can do is let us know where they got the materials!
Oh, in case you were wondering, a theodolite is “A portable surveying instrument, originally for measuring horizontal angles, and consisting essentially of a planisphere or horizontal graduated circular plate, with an alidad or index bearing sights; subsequently variously elaborated with a telescope instead of sights, a compass, level, vernier, micrometer, and other accessories, and now often with the addition of a vertical circle or arc for the measurement of angles of altitude or depression.”