Both and are guaranteed by the London scholia, so the gap is reduced to the tantalizingly small one of a monosyllabic feminine noun in the accusative case, most probably of four letters. The number of possibilities cannot be unlimited. My own suggestion must necessarily remain in limbo in the present state of our knowledge concerning the poet or poets whom Callimachus is talking about, but at least it seems to me less bizarre than other restorations currently in the field.