Language progressively changes over time.  In theorising how a language changes, scholars look at two things – internal and external change.  Internal change relates to grammar – word patterns (morphology), sound patterns (phonetics) and meaning patterns (semantics) etc.  External change relates to influences from innovations (such as the printing press), politics and social identity (such as a group of people unifying into one nation), and ‘contact’, meaning the immigration and the meeting of peoples.

Since language evolves continuously it can be hard to pinpoint where one language ends and another begins.  To make language easier for us to study, scholars have marked certain ‘language periods’ according to historical events, political or social movements, or comparison of surviving texts.

When it comes to the Vikings shaping the English language, scholars mark an ‘historical event’ to represent the start of the language period.  This event is also the first ‘contact’ where ‘external change’ begins – Scandinavian directly influencing English.  In 793AD (the 8th June to be exact) the first ‘pillage and plunder’ attack on a British monastery, Lindisfarne, by a gang of sea-fairing, red headed, brutish fellows, was recorded.  The attack made shock-waves throughout Europe: ‘Never before has such an atrocity been seen!’, wrote Alcuin of York.  This first contact also marks the start of the Viking Age.

Scandinavian (also called ‘Old Norse’) is considered to be the most important external influence on the English language.