Vilna Gaon Commentary
THE ISLES OF THE WEST
An important agent for the introduction of foreign elements was Abba-Abbas who was an uncle of Mohamed. Aba Abas had been instructed by a Jewish apostate. He added quite a lot to Moslem lore and much of what he added had been lifted straight out of Jewish Rabbinical texts and related popular sources. Abba Abas said that the "Sons of Moses" were in the far east in Gabrassa and in the far west in Gabalk. These terms are considered to be Jewish in origin. Gabrassa relates apparently to Turkestan in east Scythia where the ancestors of the Anglo-Saxons and others had sojourned for some time prior to continuing westward in the era 200-400 CE with "Scandinavian" offshoots coming later. "GABALK" was an Arabic term for western Europe especially the Frankish realm of France.
Josephus in his paraphrase of the Prophecy of Balaam, gives the prophecy as saying:
Flavius Josephus: Antiquities of the Jews - Book IV ch.4 s.6
"The multitude of your posterity also shall live as well in the islands as on the continent, and that more in number than are the stars of heaven."
Syriac MS B "The History of the Sons of Jonadab, the Son of Rechab, who are in the Midst of the Ocean, the Great Sea, When God Showed Them to Zosimus, the Virtuous Hermit"
HaGaon from Vilna (in his Commentary to Shir Ha-Shirim ("Song of Solomon") 6:5,
"The Children of Moses ("Bnei Moshe") who are beyond the Sambation, they are righteous and greatly abstentious. They are the Saviors of whom it was said,
Obadiah (ERV) 1:21 "And Saviours shall come up on mount Zion to judge the mount of Esau."