Although we are here not primarily concerned with the historical and sociolinguistic dynamic that established the Middle English dialects, the sociolinguistic history of population contact and diffusion which underlie them is a matter of considerable interest, and it sheds light on why the dialect difference we have uncovered should exist. Specifically, we will see that the northern dialect of English most likely became a CP-V2 language under the extensive contact it had with medieval Scandinavian, contact that resulted from the Danish and Norwegian population influx into the north of England during the late Old English period. In the course of its history, English has been more heavily influenced by Scandinavian than by any other language. The only comparable influence was the effect of French and Latin on the literary and learned vocabulary, but these languages influenced English grammar hardly at all. The strength of Scandinavian influence resulted from the large numbers of Norwegians and Danes who settled in England in the three centuries before the Norman Conquest (Stenton 1967, Geipel 1971). The Viking seafarers that harassed the British Isles from the 9th to the 11th centuries came at first to plunder but eventually stayed permanently. For long periods in the 9th and 10th centuries, the Danes or Norwegians ruled extensive kingdoms in England, and place name evidence indicates that the population of several shires was predominantly Scandinavian (Darby 1936, Ekwall 1936, Geipel 1971). Since the first settlers were soldiers of the Danish armies that plundered the English coastline, there must have been a great deal of intermarriage and intimate language mixture; but there were also substantial numbers of immigrants who came later, after areas of foreign control were established. Among these were substantial numbers of women as well as men (Stenton 1967:513). In the northwest of England, the major focus of Norwegian settlement, the settler-invaders came from already established Norse settlements in Ireland and may often have come as families. Moreover, in that region the density of Anglo-Saxon settlement was low and the newcomers necessarily formed a majority of the population in many places (Ekwall 1936). The linguistic effect of this combination of population movement and population mixture was extensive, comparable in some ways to the pidginization/creolization phenomena of more recent centuries, though not as extreme (see, however, Thomason & Kaufman 1988 for a more conservative assessment).
It is well known that many originally Scandinavian vocabulary items were borrowed into northern English; for example, Scandinavian `egg' for Old English (and general West Germanic) `ey', Scandinavian `sister' for Old English `swuster', and so forth. Most significantly for our purposes, several of the borrowings from Scandinavian were of closed class items which functioned mainly as morphosyntactic signals of grammatical relations. For example, the third person plural pronoun `they' was borrowed into northern English from Scandinavian and spread over time into other dialects (Morse-Gagné 1992, 1993 and the references cited there). Similarly, the anaphoric noun `same' is Scandinavian in origin. Other grammatical forms remained restricted to the North and never became general. The Middle Scots demonstrative system, for instance, contains an important Scandinavian element (Morse-Gagné 1993). Also, northern texts often show `till' for `to' as a preposition and `at' as a complementizer introducing both tensed clauses and infinitives (McIntosh, Samuels Benskin 1986). These features are clearly borrowed from Scandinavian, and so may be the use of an empty complementizer to introduce relative clauses and object complement clauses (Jespersen 1938). Another important effect of Scandinavian contact on northern English, which will play an important role in our discussion (see section 7), was to reduce the number of distinct person/number agreement endings on the finite verb.
Regarding the grammar of V2, the situation is quite complex. Unfortunately, we have no direct evidence regarding the syntax of the Scandinavian languages of the contact period. However, the extensive grammatical influence of Scandinavian on northern English indicates that the V2 grammar of the dialect could also have been affected by contact; and there is certainly no other apparent reason for the grammar of V2 in the North to differ from that in the South. The main difficulty with this hypothesis is that it is likely that Old Norse was an IP-V2 language, since modern Icelandic is of that type and is very close in its syntax to that of Old Norse in the period for which we have records (from the 12th century onward). If so, the influence of Scandinavian in producing the CP-V2 system of the North could only have been indirect. We will give evidence of just such an indirect effect; but to do so we must first develop an analysis of the V2 phenomenon in Old English, out of which the northern system evolved. We now turn to this matter, which is a difficult one and will require extensive discussion.