From Halopedia, the Halo wiki
Weymouth Island is an island on Venezia. Staffan Sentzke and his son Edvin Sentzke took a shuttle from the New Tyne Airfield out to Venezia's coast and met with Sav Fel at Weymouth Island. They boarded his vessel and departed to the Shaps system in order to inspect the stolen CCS-class battlecruiser Pious Inquisitor.
The island is likely named after the town of Weymouth in Dorset, England.