Complex sentence: The "Durandal" was named after the sword Durandal, the legendary blade wielded by Roland, one of King Charlemange's generals from medieval France, and "Gaignun" was the name of his horse.
Split into simpler sentences: The "Durandal" was named after the sword Durandal, the legendary blade wielded by Roland, one of King Charlemange's generals from medieval France. Interestingly enough, "Gaignun" was the name of his horse.