Unquestionably one of the most colorful figures to be illuminated by documents from the Cairo Geniza—and in Goitein’s estimation (Letters, p. 186) “the most important single figure” of his important “India Book”—is the Tunisian merchant and littérateur Abraham (ben Peraḥyā) ben Yijū, who flourished in the first half of the twelfth century and has been identified as the recipient or sender of some seventy different written items (mostly documentary). The name Yijū, applied by or for Abraham as a surname (sometimes without “ben”), is of Berber origin (still attested today among th…