Shem is the son of Noah traditionally associated with the ancestors of the Hebrews.
Genesis 10 presents a genealogy in which Shem is an ancestor of Eber, and the name “Hebrew” is traditionally connected with Eber. Genesis later traces the line from Shem through Arpachshad, Shelah, Eber, Peleg, and other generations to Abraham.
This genealogy is why the term “Semitic” was later formed from Shem’s name, although modern linguistics uses “Semitic” for a language family rather than as a simple biblical family label. Hebrew belongs to the Semitic language family.
Shem is one of Noah’s three sons, alongside Ham and Japheth. The association concerns biblical genealogy and tradition; it is not a claim that modern populations can be reduced to three literal family branches.