The English language, not unlike England's royal family, has Germanic origins, but numerous influences have
changed it over the years. These influences include those who invaded Britain, such as the Romans, the Vikings and the Normans, and those whom the British invaded, such as India. Oddly enough, most language experts don't think English was influenced much at all by Celtic languages, like Welsh and Cornish, even though these languages were spoken on the very same small island. Few words from those languages made their way into English.
Linguist John McWhorter sees things a little differently in his book Our Magnificent Bastard Tongue. Language is not just words, but also grammar, and it is here where McWhorter finds the Celtic influence. His prime example: the meaningless do.
In English we use words like do, did, don't and didn't all the time, even when they serve no purpose. As he points out, we could more easily just say, "I not notice" instead of "I did not notice." It might sound odd to us at first, but we could quickly get used to it. The word did, McWhorter says, serves no purpose in the sentence.
So why is English virtually the only language in the world that employs words like do and did? No other Germanic language uses them, but they are used in Welsh and Cornish. McWhorter says the English picked up the meaningless do from their neighbors, even while ignoring most Welsh and Cornish words.
"English is not normal," McWhorter writes. "It is a mixed language not only in its words, but in its grammar. Every time we say something like Did you see what he's doing?, we are structuring our utterance the way a Welsh or Cornish person would in their own native tongue."