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The answer given on the Movies and TV site could be useful to you. Basically, George RR Martin invented "Ser" to add some difference between his novels and the real world.
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/44761 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/