On the Term ‘People of the Book’

Is the term ‘People of the Book’ something that the founder of Islam dreamed up or did he take and use an existing term?

In a Hebrew dictionary we find under: עם הספר

כינוי לעם היהודי, עם ישראל, which may be translated ‘A nickname for the Jewish people, the people of Israel.’ And: עם הספר הוא כינוי לעם ישראל, עמו של ספר הספרים, הוא התנ"ך. מתוך ויקיפדיה ‘People of the Book, that is, a nickname for the people of Israel, the people of the Book of Books, that is, the Tanakh. From Wikipedia.’ Source: https://milog.co.il/%D7%A2%D7%9D_%D7%94%D7%A1%D7%A4%D7%A8

Did the term originally refer to, and only to, the Jews?