The chronicler Esteban de Garibay (1533-1599) is known in Historiography of Linguistics because of his contribution to the development of the apologist Basque tradition (Zubiaur 1989; Anchustegui 2011). However his book Los quarenta libros del Compendio Historial de las Chronicas y universal Historia de todos los Reynos de España, published in 1571, also involves the strengthening of a hypothesis about the primitive language of Spain which is relatively unknown, i.e. the theory of Hebrew. Together with his defense of Basque as first language of the Iberian Peninsula, we find a broad argumentation that intends to show a view of the ancient Spain where the Semitic element, Hebrew or Chaldean, had an important role. In this sense, we have to remember Garibay’s relationship with Toledan converso population and also his work as genealogist and his manuscript entitled Nobleza y estado de las Grandezas de España. In this paper I study the way in which Garibay’s work brings together Basque hypothesis with Hebrew and Chaldean theories, as well as the treatment of the possible sources.