By Anatoly Liberman
I have not yet met anyone who knows the word theodolite. It is absent from the memory of my computer, though dictionaries list it and encyclopedias provide illustrations of this surveyors’ instrument for measuring horizontal and vertical angles. When I explain what the word means, I usually hear the question: “Is it the same thing as a level or bubble?” Well, not quite: just look at the picture in The Century Dictionary or Wikipedia. The instrument’s name arose in England, but it seems to be better known in Germany and other European countries than at home. Since most of our readers live happily without being aware of the word theodolite, why bother? Because at one time its origin was a matter of a protracted discussion. It began in 1798 on the pages of The Gentleman’s Magazine, in the letters to its immortal editor “Mr. Sylvanus Urban” (initially the amusing pseudonym of Edward Cave). And an excellent journal it was (1731-1907). I have mined the entire set for my database and enjoyed reading the florid letters, highbrow reviews, and vituperative comments printed there. Later the debate over the etymology of theodolite was continued in the pages of Notes and Queries and with less vigor in The Philosophical Magazine. Mid-19th-century German books on geometry also devoted some space to the derivation of theodolite. I have 31 citations (counting only articles) on the subject. A word that aroused so much interest in the past (even such greats as Frank Chance and Walter W. Skeat participated in the exchange) will hardly leave the modern audience indifferent. (Those who have no idea what a wonderful scholar Frank Chance was will find some information in my early post on the unsung heroes of etymology. I hope to talk some respectable press into publishing a book of his letters to Notes and Queries. Skeat collected his myriad notes, but Chance, most unfortunately, did not, and that is why no one seems to remember him. The moral is: Produce a monument for yourself while you are alive.)
Theodolite, along with a description of the instrument, first appeared in A Geometric Practice Named Pantometria by Leonard Digges, published posthumously by his son Leonard Digges (1571). The word occurring in the book has the Latinized form theodelitus. A long excerpt from Pantometria will be found in the OED. There is every reason to believe that the word, like the instrument, was Digges’s invention, but he left no explanation on this score, and neither did his son. One of the guesses that circulated in the literature may be correct, but we will never know for sure. This is natural. Every word must have been coined by someone, though we seldom realize that an etymologist always follows the tracks of an individual “wordsmith” whose coinage became with time common property and changed its shape. Gas, gnome, Lilliputian, Jeep, and boondoggle (to mention a few famous examples) have known “authors,” but we still argue over their origin. Many instruments have enigmatic names. One of them is skirret (it is used for measuring land, aligning trenches, etc. working on a revolving center-pin). A mason’s term, it surfaced in a special book in the middle of the 19th century, and no one seems to know where it came from.
Three approaches to theodolite have been tried. 1) The word has a strong Greek look, so that attempts to decompose it into two or three Greek elements need not surprise us: thea “prospect” + delo– “make visible”; theaomai “see” + dolos “stratagem” or + dolikhos “long,” or + delos “manifest” + itus “circumference.” Or perhaps the last syllable should be understood as litos “simple; smooth” (theomai “see” + odos “path” + litos = “scanner of exact (or finely drawn) lines of direction.” Conversely, –litus may be equal to Greek lithos “stone” (compare Engl. monolith); then we obtain “stone devised as a path to good observation.” The common feature of those etymologies is the root meaning “see.” Or take obelos “pointed stick, rod, spit” (as in obelisk), transmute it into Aeolic odelos, and get odelited “graduated,” whatever, th– means (perhaps the English definite article). Still another possibility is theou + dolos “god’s counsel”: “As the astrolabe had its derivation from the Greek astro and labe, taking the stars, the inventor of the theodolite thought he could do no less that seek in that language for some equivalent for Jacob’s staff” (actually, dolos means “bait; trap”). Some of the aforementioned proposals are fanciful, while the others are not unreasonable. If –us is a spurious Latin ending, litos and lithus present no interest as putative components of theodolite. In the original edition of the OED we read: “Can it have been (like many modern names of inventions) an unscholarly formation form theomai, I view, or theo, behold, and delos, visible, clear, manifest, with a meaningless termination?” Needless to say, all the sources quoted above use Greek letters with proper accent marks.
(2). “Theodelitus’…consists of a graduated circle, with a diametral [sic] bar, furnished with a couple of sights. This bar always had the name of alhidada, or alidade…. Now theodelitus has the appearance of being a participle or adjective; and may therefore seem to refer to the circle as descriptive of an adjunct. A circle with alidade: could it be possible that, in the confused method of forming and spelling words which characterised the vernacular English science of the sixteenth century, an alidated circle should become theodelited?” (Professor A. De Morgan, 1863). This hypothesis (theodolite as an Arabic word; th– as the article) had a few supporters and has been periodically revived. However, it is hopelessly convoluted and presupposes numerous changes, which are the more surprising as alhidada, an old word in English, never appeared in the garbled form reconstructed by De Morgan. Frank Chance disposed of this etymology in his typically ruthless way.
(3) As early as 1865 it has been suggested that the word theodolite goes back to the proper name Theodolus. One of its bearers was active in 1685, much too late for Digges, but Theodolus’s family had a reputation for being good mathematicians (J.C.J.). Skeat, writing in 1895, did not remember the old note, for he stated: “My own guess… is quite a new one, unlike any that has ever yet been suggested. My belief is that it [the word] is derived from the personal name Theodolus, which, as every schoolboy knows, means ‘servant of God’.” Today not every schoolboy knows the meaning of Theodolus (in British public, that is, private schools of Skeat’s day, there even existed a slang word dolos “slave”), but one thing is certain: an etymologist can never be sure that his (or her) conjecture is new. At that time, Skeat had no clue to the persona of the mysterious Theodolus. However, this is the pronouncement in the last edition of his dictionary: “Generally said to be Greek. Formerly theodelitus, meaning “a circle with a graduated border; used A.D. 1571. Also theodolet, theodelet. Apparently imitated (it is not known why) from Old French theodelet, theodolet, the name of a treatise, literally ‘a work by Theodulus’.” Earnest Weekley offers a similar version of this etymology: “It is just possible that Digges, for some fantastic reason now unknown, named the instrument after the famous Old French theological poem called the Tiaudelet, translated from the Late Latin Theodulus (9 century).”
A sorry tale: a forgotten word of undiscovered origin. It reminds me of old pictures one sometimes sees in great museums: “Portrait of an unknown man by an unknown artist.”
Anatoly Liberman is the author of Word Origins…And How We Know Them as well as An Analytic Dictionary of English Etymology: An Introduction. His column on word origins, The Oxford Etymologist, appears here, each Wednesday. Send your etymology question to email@example.com; he’ll do his best to avoid responding with “origin unknown.”