The name Semite comes from Shem, eldest of the three sons of Noah. In the Greek and Latin versions of the Bible, Shem becomes Sem, since neither Greek nor Latin has any way of representing the initial sound of the Hebrew name.

https://www.myjewishlearning.com/article/who-are-the-semites/

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Semites, Semitic people or Semitic cultures (from the biblical "Shem", Hebrew: שם‎) was a term for an ethnic, cultural or racial group who speak or spoke the Semiticlanguages. ... The term "Semites", together with the parallel terms Hamites and Japhetites, is now largely obsolete outside linguistics.