English is a West Germanic language which originated from the Anglo-Frisian dialects brought to Britain by Germanic settlers and Roman auxiliary troops from various parts of what is now northwest Germany and the northern Netherlands. Initially, Old English was a diverse group of dialects, reflecting the varied origins of the Anglo-Saxon Kingdoms of England. One of these dialects, Late West Saxon, eventually came to dominate. The original Old English language was then influenced by two waves of invasion: the first by speakers of the Scandinavian branch of the Germanic language family, who conquered and colonized parts of Britain in the 8th and 9th centuries; the second by the Normans in the 11th century, who spoke Old Norman and ultimately developed an English variety of this called Anglo-Norman. These two invasions caused English to become "mixed" to some degree, though it was never a truly mixed language in the strict linguistic sense of the word, as mixed languages arise from the cohabitation of speakers of different languages, who develop a hybrid tongue for basic communication.

Cohabitation with the Scandinavians resulted in a significant grammatical simplification and lexical enrichment of the Anglo-Frisian core of English; the later Norman occupation led to the grafting onto that Germanic core of a more elaborate layer of words from the Romance languages. This Norman influence entered English largely through the courts and government. Thus, English developed into a "borrowing" language of great flexibility, resulting in an enormous and varied vocabulary.