Complex sentence: In 828 CE the Saracens captured the diminished remnant of the city and renamed it "Kerkent" in Arabic; it was thus Sicilianized as "Girgenti".
Split into simpler sentences: In 828 CE the Saracens captured the diminished remnant of the city. They pronounced its name as "Kerkent" in Arabic; it was thus Sicilianized as "Girgenti".