It refers to John Methuen (c.1650-1706) who served as a Member of Parliament; Lord Chancellor of Ireland; Privy Councilor; Envoy and then Ambassador Extraordinary to Portugal where he negotiated the "Methuen" Treaty of 1703 which cemented allegiances in the War of Spanish Succession and created favorable trade terms for Port wine. He is buried in Westminster Abbey.
In 1703 the Methuen Treaty was signed in Lisbon. This was a commercial treaty between Portugal and England which established that English textiles would be accepted in Portugal and that the Portuguese wines would be preferred in England, by paying only two thirds of the rates settled with the French. The Methuen Treaty of 1703 between England and Portugal played a major part in the development of the port wine industry. Preference was granted under this treaty to wines from Portugal and this provided great stimulus to the wine producers in the hinterland of Oporto. This original port is emulated today from Berkeley to Barossa.