see also Tresillian House Tresillian is a small village in the civil parish of St Clement, in mid Cornwall, England, United Kingdom. It is three miles east of Truro on the A390 road. Tresillian means "a place of eels" in the Cornish language, according to a 19th-century writer. However, modern toponymists agree that the name in fact translates as "farm/settlement of a man called Sulyen".