The sounds /w/ (spelled ?V?) and /b/ (spelled ?B?) of Classical Latin developed into a bilabial fricative /?/ between vowels in Early Medieval Latin. Therefore, ?V? no longer represented adequately the labial-velar approximant sound /w/ of Germanic phonology.
The Germanic /w/ phoneme was therefore written as ?VV? or ?uu? (?u? and ?v? becoming distinct only by the Early Modern period) by the 7th or 8th century by the earliest writers of Old English and Old High German. Gothic (not Latin-based), by contrast, simply used a letter based on the Greek ? for the same sound. The digraph ?VV?/?uu? was also used in Medieval Latin to represent Germanic names, including Gothic ones like Wamba.
It is from this ?uu? digraph that the modern name "double U" derives. The digraph was commonly used in the spelling of Old High German, but only sporadically in Old English, where the /w/ sound was usually represented by the runic ??? wynn. In early Middle English, following the 11th-century Norman Conquest, ?uu? gained popularity and by 1300 it had taken wynns place in common use.
Scribal realization of the digraph could look like a pair of Vs whose branches crossed in the middle. An obsolete, cursive form found in the nineteenth century in both English and German was in the form of an en whose rightmost branch curved around as in a cursive vee.
The shift from the digraph ?VV? to the distinct ligature ?W? is thus gradual, and is only apparent in abecedaria, explicit listings of all individual letters. It was probably considered a separate letter by the 14th century in both Middle English and Middle German orthography, although it remained an outsider not really considered part of the Latin alphabet proper, as expressed by Valentin Ickelshamer in the 16th century, who complained that
Poor w is so infamous and unknown that many barely know either its name or its shape, not those who aspire to being Latinists, as they have no need of it, nor do the Germans, not even the schoolmasters, know what to do with it or how to call it; some call it we, [... others] call it uu, [...] the Swabians call it auwawau
In Middle High German (and possibly already in late Old High German), the West Germanic phoneme /w/ became realized as [v]; this is why the German ?w? today represents that sound. There is no phonological distinction between [w] and [v] in contemporary German. Modern German dialects generally have only [v] or [v] for West Germanic /w/, but [w] or [??] remains heard allophonically for w, especially in the clusters ?schw?, ?zw?, and ?qu?. Some Bavarian dialects preserve a "light" initial [w] in words like wuoz (Standard German weis [va?s] [I] know). The Classical Latin [?] is heard in the Southern German greeting Servus (hello or goodbye).
In Dutch, it became a labiodental approximant /v/ (with the exception of words with -?eeuw?, which have /e??/, or other diphthongs containing -?uw?). In many Dutch speaking areas, such as Flanders and Suriname, the /?/ pronunciation is used at all times.
In Europe, there are only a few languages that use W in native words and all are located in a central-western European zone between Cornwall and Poland. English, German, Low German, Dutch, Frisian, Welsh, Cornish, Breton, Walloon, Polish, Kashubian, Sorbian and Resian use W in native words. English uses W to represent /w/, German, Polish and Kashubian use it for the voiced labiodental fricative /v/ (with Polish and related Kashubian using L for /w/), and Dutch uses it for /v/. Unlike its use in other languages, the letter is used in Welsh and Cornish to represent the vowel /u/ as well as the related approximant consonant /w/. English also contains a number of words beginning with a written W that is silent in most dialects before a (pronounced) R, remaining from usage in Anglo-Saxon in which the W was pronounced: wreak, wrap, wreck, wrench, wroth, wrinkle, etc. (Certain dialects of Scottish English still distinguish this digraph.)
In the International Phonetic Alphabet, /w/ is used for the voiced labial-velar approximant, probably based on English.
In Finnish, ?W? is seen as a variant of ?V? and not a separate letter. It is however recognised and maintained in the spelling of some old names, reflecting an earlier German spelling standard, and in some modern loan words. In all cases it is pronounced /v/.
In Danish, Norwegian and Swedish, ?W? is named double-v and not double-u. In these languages, the letter only exists in old names, loanwords and foreign words. (Foreign words are distinguished from loanwords by having a significantly lower level of integration in the language.) It is usually pronounced /v/, but in some words of English origin it may be pronounced /w/. The letter was officially introduced in the Danish and Swedish alphabets as late as 1980 and 2006, respectively, despite having been in use for much longer. It was recognized since the conception of modern Norwegian, with the earliest official orthography rules of 1907. ?W? was earlier seen as a variant of ?V?, and ?W? as a letter (double-v) is still commonly replaced by ?V? in speech (e.g. WC being pronounced as VC, www as VVV, WHO as VHO, etc.) The two letters were sorted as equals before ?W? was officially recognized, and that practice is still recommended when sorting names in Sweden. In modern slang, some native speakers may pronounce ?W? more closely to the origin of the loanword than the official /v/ pronunciation.
In the alphabets of most modern Romance languages (excepting far northern French and Walloon), W is used mostly in foreign names and words recently borrowed (le week-end, il watt, el kiwi). The digraph ou is used for /w/ in native French words; oi is /wa/ or /w?/, oin is /we?/. In Spanish, Italian, and Portuguese, [w] is a non-syllabic variant of /u/, spelled U (with a diaeresis in the Spanish combinations gue and gui).
In the Cyrillic alphabet used for the Belarusian language, ??? is pronounced like English /w/.
The Japanese language uses "W", pronounced /daburu/, as an ideogram meaning "double".
In Arabic, "W" is transliterated using the penultimate letter of the alphabet, ? (waw).
In Italian, while the letter "W" is not considered part of the standard Italian alphabet, the character is often used in place of Viva (hooray for...), while the same symbol written upside down indicates abbasso (down with...).
In Vietnamese, W is called , from the French . It is not included in the standard Vietnamese alphabet, but it is often used as a substitute for qu- in literary dialect and very informal writing.
W is also the symbol for the chemical element tungsten, after its German (and alternative English) name, Wolfram.
"Double U" is the only English letter name with more than one syllable, except for the occasionally used, though somewhat archaic, Å“ (its name is pronounced similar to ethel), the formerly common in print &, ampersand, and the archaic pronunciation of Z, izzard. The initialism "www" for the World Wide Web thus, perhaps ironically, has three times as many syllables as the full name.
Some speakers therefore shorten the name "double u" into "dub" only; for example, University of Wisconsin, University of Washington, University of Wyoming, University of Waterloo, University of the Western Cape and University of Western Australia are all known colloquially as "U Dub", and the automobile company Volkswagen, abbreviated "VW", is sometimes pronounced "V-Dub". The fact that many website URLs still require a "www." prefix has likewise given rise to a shortened version of the original, three-syllable pronunciation. With the arguable exception of the letter H, W is currently the only English letter whose name is not pronounced with any of the sounds that the letter typically makes. Many others, however, pronounce the "w" as dub-u, reducing it to two syllables. For example, "www" would be six syllables rather than nine, being pronounced, dub-u dub-u dub-u.
In other Germanic languages, including German, its name is similar to that of English V. In many languages, its name literally means "double v": Portuguese duplo ve, Spanish doble ve (though it can be spelled uve doble), French double ve, Icelandic tvofalt vaff, Czech dvojite ve, Finnish kaksois-vee, etc.
George W. Bush has been given the nickname "Dubya", after the colloquial pronunciation of the name of "W" in Texas.1 Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.