I'm not sure I understand you. If you are talking about the coming in existence of the English language, I'd say: "The (birth, emergence, or development) of what would eventually evolve into the modern English language." There was Old English, which was a separate language (even with different letters). And that evolved into different kinds of middle English. Chaucer might have written in middle English. It can be almost unintelligible to a modern reader.

I think you want to know the history of English Language.