It will quickly dawn on even the most linguistically incurious student that in terms of vocabulary, English is a mongrel tongue, a hodge-podge of Germanic and French and Latin etymologies, with more than a little Celtic and Viking and Aztec and Bengali thrown in. There is little the English language cannot digest and regurgitate in the way of new vocabulary.
But structurally? With some exceptions (the Celtic do question auxiliary, for example) English is usually taken to be a West-Germanic language, closely related to modern German and Dutch. The progenitors of our language, we are given to understand, were the Angles and Saxons from Frisia and Anglia, arriving in Britain from the late fifth century. Whatever languages came later – Old Norse and Norman-French – were grafted on to this stock.
But there are other theories. From the early ninth century, Britain was subject to waves, first of attacks, later of settlement, by the Vikings. The Norsemen came to dominate the island politically in the North and East (the so-called Danelaw); the South and South-West resisted the Viking incursions, and Old English remained the dominant tongue.
We know, however, that Middle English (the English of the Middle Ages) developed from the East Midland dialect, and the East Midlands was substantially in the Danelaw. The conclusion follows that Old English died out, and Old Norse, or the variant of it spoken in the North and East of England, laid the foundations for modern English.
This would explain why many elements of modern English grammar resemble Norwegian and Danish more than they resemble German and Dutch – objects follow compound verbs, for example (I have read the book, not I have the book read); and prepositions dangle at the end of sentences (who did you go to the pub with?). It would also explain why a great many common words (egg, knife, anger) are of Old Norse and not Old English origin (although not, admittedly, why the reverse is also true).
The theory (first put forward in 2012 by Jan Terle Faarland and Joseph Emmonds of the universities of Oslo and Palacký respectively) has not, I should say, gained general acceptance; but then, there is a lot of entrenched scholarship to overcome. It is, however, more than a little appealing to think of ourselves (linguistically, not racially) as remnant Vikings, distant cousins to all those Norse sagas and seafaring hoodlums, washed up on British shores.