a single word which follows the rules defining a legal XML name (see https://www.w3.org/TR/REC-xml/#dt-name), supplying a name to specify which index (of several) the index entry belongs to.
David's other principal backer, Josiah ha-Kohen <index indexName="NAMES"> <term>Josiah ha-Kohen b. Azarya</term> </index> b. Azarya, son of one of the last gaons of Sura <index indexName="PLACES"> <term>Sura</term> </index> was David's own first cousin.