The document discusses three major influences on the English language: Celtic, Latin, and Scandinavian. It analyzes the influence of each in detail, noting the influx of vocabulary from each source, especially place names from Celtic and religious/scholarly terms from Latin. The Scandinavian influence is discussed in the context of the Viking invasions, noting sound changes like the retention of hard 'k' and 'g' sounds in borrowed words. Overall, the document provides an overview of the three key external influences that shaped the early development of the English language.