If you were transported unconscious to a foreign country and then wakened in the street, a glimpse of this plumber’s van would tell you exactly where you were—only Icelandic contains the two unusual letters that feature in that first word viðhaldsþjónusta (“maintenance services”). In fact, the Icelanders refer to their letters ð and þ as séríslenskur: “uniquely Icelandic”.

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The þ character is called thorn in English, and it derives from the ancient runic alphabet once used by speakers of the Germanic languages (which include the languages of Scandinavia). Below, it appears as the third letter of the Elder Futhark, the earliest known version of runic, which prevailed in northern Europe for about the first eight hundred years of the Christian Era:

The þ rune was associated with the dental fricative sound now symbolized by “th” in English. In fact, the name Futhark for this alphabet comes from the pronunciation of its first six letters. (Be sure to pronounce the first syllable “foo” rather than “fuh”.)

The letter’s name in proto-Germanic has been reconstructed as something like þurisaz, meaning “giant”. If you want to know how complicated it is to figure something like that out, take a look at the first few minutes of this video, by Jackson Crawford, a historical linguist:

The letter acquired its modern English name, thorn, when the Elder Futhark was modified by the Anglo-Saxons, and used to write Old English (among other languages). Elsewhere, the Elder Futhark gave way to (you guessed it) the Younger Futhark, which was used to write various Scandinavian languages.

When languages that used the thorn rune started being written in the Latin alphabet, the old runic letter was retained, but its shape shifted from the incised straight lines of runic to a more rounded version suited to pen and ink.*

But the Latin alphabet already had a conventional way of indicating the dental fricative sound that thorn symbolized in runic—the Romans had used the “th” digraph when they transliterated Greek words containing the letter θ (theta) into Latin. So thorn gradually faded out of use, being replaced by “th” in every language but Icelandic.

The fading of thorn in English took an odd turn, however. As Old English evolved into Middle English, generations of scribes gradually modified the thorn letter so that its upper stem shortened and then disappeared, and the bowl of the letter opened at the top. What was left looked very like a letter y. For instance, here are the opening words of the Gospel of Saint John in a fourteenth-century Wycliffe’s Bible:

“In the beginning …” is written as “In þe bigynyng …” But the open-topped þ is so like the subsequent y characters, that the scribe has felt obliged to indicate the y‘s by adding a dot or a line above each.

Thorn then drifted almost entirely out of use, being retained only in a few small grammatical words—for instance, “the” was written þe, and “this” and “that” were abbreviated as þs and þt. Written down, they looked very like ye, ys and yt. Here are the latter two, looking like Y^S and Y^T, appearing in the inscription on Shakespeare’s funerary monument in the Holy Trinity Church in Stratford-upon-Avon:

The thorn characters are rendered identically to the letter y as it appears elsewhere in the same text. So it was natural that when the word “þe” appeared in printed books, many English printers, finding no thorn character in their imported continental type-boxes, used a letter y instead.

Which is why the world is still full of shops and pubs called “Ye Olde …” something-or-other.

That “ye” should be pronounced “the”, and it’s the very last gasp of the runic character thorn in English.

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Although the thorn character was imported, the edh has its origins in the Latin alphabet. (It’s also spelled eth. Either way, pronounce its name with a voiced “th”, as in the first syllable of weather.) Edh first appeared in Old English, and the curved shape of its lower-case form (ð) preserves the curved shape of a lower-case d in the uncial script of Ireland. Scribes took the uncial d, and crossed its ascender, like this:

Its name in Old English was ðæt, which is often rendered as that in the modern English alphabet. The Oxford English Dictionary has no record of the name edh before the nineteenth century—presumably it was coined in imitation of its sound.

And that’s the odd thing about edh and thorn—they were both used to symbolize the same dental fricative sounds in Old English. Sometimes a scribe would even shift the spelling of a word from one letter to the other, halfway through a manuscript. It’s no surprise that one eventually won out—edh disappeared from English in the fourteenth century; thorn persisted for a while in a Middle English (as described above), before surrendering its job to “th”.

The mediaeval Scandinavians borrowed the edh for their own alphabets, but gradually replaced it with “dh” or just plain d. Even Icelandic mislaid the edh for centuries—for example, it is not mentioned in the First Grammatical Treatise, a twelfth-century work on the phonology of Old Icelandic, in which thorn performs solo duty in representing the dental fricative sounds. But edh was restored when the Icelandic alphabet was finalized in the nineteenth century. Edh and thorn now have complementary roles, representing the voiced and unvoiced dental fricatives, respectively. So edh is the hard “th” sound at the start of that, while thorn is the soft “th” sound at the start of, well, thorn.^†

Once Icelandic got the ball rolling for edh, the letter was revived in a couple of other languages, too. An alphabet for Faeroese was adopted in 1854 (it had languished unwritten for centuries), and it included the edh on mainly etymological grounds. Written Faeroese contains an edh where a dental fricative would have been sounded in Old Norse—but that sound is absent from modern Faeroese, so the edh most often signals a gliding link between two vowels. The placename Viðareiði is pronounced something like VEE-ya-rye-ih, for instance. (The fact that written Faeroese preserves some of the appearance of Old Norse, from which Icelandic also evolved, means that Icelanders can often puzzle out written Faeroese despite being unable to understand the spoken language.)

More recently, the Elfdalian language of Central Sweden (with around 2500 speakers) acquired its own alphabet in 2005—the edh does duty for the voiced dental fricative, just as in Icelandic.

And that’s it for edh—three languages, of which Icelandic is by far the most commonly spoken. It’s also used as a phonetic symbol in the International Phonetic Alphabet, indicating a voiced dental fricative. The unvoiced dental fricative, for which Icelandic uses the thorn character, is indicated phonetically by the Greek letter θ (theta).

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So edh is not as “uniquely Icelandic” as the Icelanders might claim, but they do speak the only modern language that uses the letter thorn.

Strangely, the BBC did recently try to insert the thorn into Turkish. Michael Scott’s fascinating television series Ancient Invisible Cities visited Istanbul for Series 1 Episode 3, which was broadcast just as I was putting the finishing touches to this post. With amazing synchronicity, and to my initial alarm and subsequent amusement, some strange orthographic misadventure in the bowels of the BBC converted the family name of the Turkish art historian Ferudun Özgümüş into Özgümüþ.

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* For the runic and uncial illustrations on this page, I’m using the excellent Pfeffer Mediæval font.
^† You might wonder if edh and thorn performed similar duties, indicating different sounds, in Old English—but that seems not to be the case. They were treated as entirely interchangeable characters, and the reader was left to work out the voiced/unvoiced distinction for themselves, just as we do today with the “th” digraph, which stands for both voiced and unvoiced sounds.