 The settlement of Plympton , further up the River Plym than the current Plymouth , was also an early trading port , but the river silted up in the early 11th century and forced the mariners and merchants to settle at the current day Barbican near the river mouth . At the time this village was called Sutton , meaning south town in Old English . The name Plym Mouth , meaning " mouth of the River Plym " was first mentioned in a Pipe Roll of 1211 . The name Plymouth first officially replaced Sutton in a charter of King Henry VI in 1440 . See Plympton for the derivation of the name Plym . 
