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.”


  1. I only found out the meaning of this word recently. I knew it all my life from an old favourite film, Carry on Behind (1974). Kenneth Williams has just been in an accident, and Windsor Davies breaks one of the legs off a tripod to make a splint.
    KEN: Ooh, no! Me theodolite’s brooooken!
    WINDSOR: Then we’d better put a splint on that as well!

  2. Funny, just came across a theodolite tonight in B. S. Johnson’s novel, Christie Malry’s Own Double Entry”:
    “The Shrike’s Old Mum lived, as you already know, up in Islington. Islington is certainly up from Hammersmith, which is only sixteen feet above sea level, whereas old Islington lies mainly on a ridge whose southernmost part is Claremont Square in Finsbury. The exact height of Claremont Square escapes me for a moment, though I could look it up. Yes, I will. It is just above the hundred foot contour line, say fifteen feet, making it a height of a hundred and fifteen feet in all. Claremont Square must have been a fine point to view the city and the river at one time, before it was built on. But of course that is not really relevant for our purposes, since the Shrike’s Old Mum lived just on the eastern side of the ridge, down off Essex Road, at the flats in Britannia Row. And I am not going out with a theodolite and mate to determine just where she lived in relation to the hundred foot contour line, or to work out how high her flat took her above it in relation to ground level; no, not for you; nor anyone.”
    In another place, the narrator manages to employ the words “trituration,” “helminthoid,” “cryptorchid,” and “eirenicon” in a single paragraph.

  3. Sounds like my kind of book!

  4. I tend to forget the meanings of words like that [new ones push the old ones away I think], but I can’t forget the meaning of the theodolite because according to my father the correct name of the device in Russian is “Теодолит и дальномер” (which then sounded more like “теодолитый дальномер” to me) and the two sit together somewhere in my memory ever since.

  5. There’s a theodolite in Paul Muldoon’s ‘I Remember Sir Alfred’, from his third collection Why Brownlee Left (1980). It’s a great poem. This is the third stanza of five:
    The spirit of Sir Alfred McAlpine
    Paces the meadow, and fixes his theodolite
    On something beyond the horizon,
    Love, or fidelity.

  6. John Keay in his book “The Great Arc” or The Dramatic Tale of how India was Mapped and Everest got his name explains the difficulties of surveying India and using the “Great Theodolite” manufactured by Carey in England.
    Unfortunately no explanation of the origin of the word or instrument – possibly German or French reading between the lines.

  7. John Cowan says

    Wikt accepts the al-`idada etymology:

    From New Latin theodolitus (1571), perhaps containing Ancient Greek θέᾱ (théā, “sight, view”) and Arabic العِضَادَة‎ (al-ʕiḍāda, “astrolabe, alidade”); if so, doublet of alidade.

    The OED has not yet updated its etymology.

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