Simplify the following text for a Grade 12 native English-speaking person.
Original: Lager Helgoland was a Nazi concentration camp on Alderney in the Channel Islands , named after the Frisian Island of Heligoland ( in German , Helgoland ) , a former British possession handed over to Germany in 1890 .
Simplified: Lager Helgoland was a Nazi concentration camp on Alderney in the Channel Islands , named after the Frisian Island of Heligoland , a former British possession handed over to Germany in 1890 .