Saturday's curiosity question

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My husbands form of relaxing is to watch all these shows on cable, real or fiction. I've noticed there is no use of "R"s during the viking days, on the US east cost and in the deep south. So if the English language, alphabet, etc, came along long after it was spoken, where on earth did the "R" come from and why? I'm thinking there is someone here with this knowledge, maybe. I'm just curious!