When did the Old Norse language originate?
22666#1
The Proto-Norse language developed into Old Norse by the 8th century, and Old Norse began to develop into the modern North Germanic languages in the mid- to late 14th century, ending the language phase known as Old Norse. These dates, however, are not absolute, since written Old Norse is found well into the 15th century.
Old Norse
337386#15
Words of Old Norse origin have entered English primarily from the contact between Old Norse and Old English during colonisation of eastern and northern England between the mid 9th to the 11th centuries (see also Danelaw). Many of these words are part of English core vocabulary, such as "egg", "sky" or "knife".
Foreign language influences in English
344148#12
The Scandinavians, or Norsemen, spoke dialects of a North Germanic language known as Old Norse. The Anglo-Saxons and the Scandinavians thus spoke related languages from different branches (West and North) of the Germanic family; many of their lexical roots were the same or similar, although their grammatical systems were more divergent. Probably significant numbers of Norse speakers settled in the Danelaw during the period of Scandinavian control. Many place-names in those areas are of Scandinavian provenance (those ending in "-by", for example); it is believed that the settlers often established new communities in places that had not previously been developed by the Anglo-Saxons. The extensive contact between Old English and Old Norse speakers, including the possibility of intermarriage that resulted from the acceptance of Christianity by the Danes in 878, undoubtedly influenced the varieties of those languages spoken in the areas of contact. Some scholars even believe that Old English and Old Norse underwent a kind of fusion and that the resulting English language might be described as a mixed language or creole. During the rule of Cnut and other Danish kings in the first half of the 11th century, a kind of diglossia may have come about, with the West Saxon literary language existing alongside the Norse-influenced Midland dialect of English, which could have served as a koine or spoken lingua franca. When Danish rule ended, and particularly after the Norman Conquest, the status of the minority Norse language presumably declined relative to that of English, and its remaining speakers assimilated to English in a process involving language shift and language death. The widespread bilingualism that must have existed during the process possibly contributed to the rate of borrowings from Norse into English.
History of English
22666#4
Old Icelandic was very close to Old Norwegian, and together they formed the Old West Norse dialect, which was also spoken in settlements in Ireland, Scotland, the Isle of Man and northwest England, and in Norse settlements in Normandy. The Old East Norse dialect was spoken in Denmark, Sweden, settlements in Kievan Rus', eastern England, and Danish settlements in Normandy. The Old Gutnish dialect was spoken in Gotland and in various settlements in the East. In the 11th century, Old Norse was the most widely spoken European language, ranging from Vinland in the West to the Volga River in the East. In Kievan Rus', it survived the longest in Veliky Novgorod, probably lasting into the 13th century there. The age of the Swedish-speaking population of Finland is strongly contested, but at latest by the time of the Second Swedish Crusade in the 13th century, Swedish settlement had spread the language into the region.
Old Norse
22666#46
The earliest inscriptions in Old Norse are runic, from the 8th century. Runes continued to be commonly used until the 15th century and have been recorded to be in use in some form as late as the 19th century in some parts of Sweden. With the conversion to Christianity in the 11th century came the Latin alphabet. The oldest preserved texts in Old Norse in the Latin alphabet date from the middle of the 12th century. Subsequently, Old Norse became the vehicle of a large and varied body of vernacular literature, unique in medieval Europe. Most of the surviving literature was written in Iceland. Best known are the Norse sagas, the Icelanders' sagas and the mythological literature, but there also survives a large body of religious literature, translations into Old Norse of courtly romances, classical mythology, and the Old Testament, as well as instructional material, grammatical treatises and a large body of letters and official documents.
Old Norse
22666#49
As Proto-Norse evolved into Old Norse, in the 8th century, the effects of the umlauts seem to have been very much the same over the whole Old Norse area. But in later dialects of the language a split occurred mainly between west and east as the use of umlauts began to vary. The typical umlauts (for example "fylla" from *"fullijan") were better preserved in the West due to later generalizations in the east where many instances of umlaut were removed (many archaic Eastern texts as well as eastern runic inscriptions however portray the same extent of umlauts as in later Western Old Norse).
Old Norse
1329694#0
Words of Old Norse origin have entered the English language, primarily from the contact between Old Norse and Old English during colonisation of eastern and northern England between the mid 9th to the 11th centuries (see also Danelaw). 
Many of these words are part of English core vocabulary, such as "egg" or "knife". 
There are hundreds of such words, and the list below does not aim at completeness.
List of English words of Old Norse origin
276308#9
The original Icelandic manuscripts which are the main source of our knowledge of Norse mythology did not employ a unified system of spelling. During the Viking Age, many dialects of Old Norse were spoken. While they appear to have been mutually intelligible, the slight variances resulted in various spelling. Thus the same name might be spelled several different ways even in the original manuscripts. Letters unique to the language existed, such as a modified version of the letter Wynn called Vend that was used briefly for the sounds , , and . In particular, the length of vowels was only sporadically marked in many manuscripts and various umlauted vowels were often not distinguished from others. Another complication is that several shortcut forms for common words, syllables, and grammatical endings developed. One example is the use of the rune named ' (man) for the word '. Another is the use of a special glyph for the various r-endings so common in Old Norse. These scribal abbreviations are categorized as follows:These abbreviation conventions and a majority of the signs are inherited from the Latin language itself, and were common to the Latin alphabet in other languages. However, other signs or conventions are specifically Norse, such as the " zig-zag.
Old Norse orthography
8569916#14
First, the waves of Norse colonisation of northern parts of the British Isles in the 8th and 9th centuries put Old English into intense contact with Old Norse, a North Germanic language. Norse influence was strongest in the Northeastern varieties of Old English spoken in the Danelaw area around York, which was the centre of Norse colonisation; today these features are still particularly present in Scots and Northern English. However the centre of norsified English seems to have been in the Midlands around Lindsey, and after 920 CE when Lindsey was reincorporated into the Anglo-Saxon polity, Norse features spread from there into English varieties that had not been in intense contact with Norse speakers. Some elements of Norse influence that persist in all English varieties today are the pronouns beginning with "th-" ("they, them, their") which replaced the Anglo-Saxon pronouns with ().
English language
33064581#7
Old Norse is a North Germanic language that was spoken by inhabitants of Scandinavia and of their overseas settlements during the Viking Age, until about 1300. Its influence on Scots island names is considerable due to the development of both the Earldom of Orkney and the Kingdom of the Isles which resulted in almost all of the inhabitable islands of Scotland (except those in the Firth of Forth) coming under Norse control from the 9th to 13th centuries.
Norn is an extinct North Germanic language that developed from Old Norse and was spoken in Shetland, Orkney and possibly Caithness. Together with Faroese, Icelandic and Norwegian it belongs to the West Scandinavian group. Very little written evidence of the language has survived and as a result it is not possible to distinguish any island names that may be Norn rather than Old Norse. After the Northern Isles were pledged to Scotland by Norway in the 15th century, the early Scottish Earls spoke Gaelic when the majority of their subjects spoke Norn and both of these languages were then replaced by Insular Scots.
Scottish island names
8227#10
From the seventh century, the common Norse language began to undergo changes that did not spread to all of Scandinavia, resulting in the appearance of two dialect areas, Old West Norse (Norway and Iceland) and Old East Norse (Denmark and Sweden). Most of the changes separating East Norse from West Norse started as innovations in Denmark, that spread through Scania into Sweden and by maritime contact to southern Norway. A change that separated Old East Norse (Runic Swedish/Danish) from Old West Norse was the change of the diphthong "æi" (Old West Norse "ei") to the monophthong "e", as in "stæin" to "sten". This is reflected in runic inscriptions where the older read "stain" and the later "stin". Also, a change of "au" as in "dauðr" into "ø" as in "døðr" occurred. This change is shown in runic inscriptions as a change from "tauþr" into "tuþr". Moreover, the "øy" (Old West Norse "ey") diphthong changed into "ø", as well, as in the Old Norse word for "island". This monophthongization started in Jutland and spread eastward, having spread throughout Denmark and most of Sweden by 1100.
Danish language
585870#6
In 1814, while still living in Iceland, he finished his prize essay, "Investigation of the Origin of the Old Norse or Icelandic Language" (1818), in which he argued that Old Norse was related to the Germanic languages, including Gothic, to the Baltic and Slavic languages, and even to Classical Latin and Greek, which he grouped together under the label Thracian. He also argued that the Germanic languages were not related to Basque, Greenlandic, Finnish or the Celtic languages (on this last instance he was wrong, and he later acknowledged this). The academy accepted the essay but suggested that he could have spent more time comparing Icelandic with Persian and other Asian languages. Because of this, Rask envisioned a trip to India to study Asian languages such as Sanskrit, which was already being taught by philologists such as Franz Bopp and Friedrich Schlegel in Germany. In 1814, after returning from Iceland, Rask worked as a sub-librarian at the University of Copenhagen library.
Rasmus Rask