"Santa Claus" The movies "Santa Clause" were a play on the word "clause", which is to do with the details of a contract (as seen in the movies).
Either way, Santa Claus is a corruption of Santa Nicolaus, i.e. Saint Nicholas.
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It originated from Saint Nicholas which evolved into Santa Claus. But if you mean the movie, a "clause" is a distinct phrase, usually one that changes the meaning of a sentence.