Toponymy
For much of its earlier history, the settlement here was known as Sutton (Sutona in 1086, Suttona in 1201), simply meaning South town. It was based near Sutton Harbour, the oldest quarter of the modern city. The modern name has two parts: Plym and mouth. The element Plym is taken from the River Plym along which it traded with its parent settlement of Plympton, but its name (first recorded as Plymentun in c.900) is considered to derive from the Old English word for 'plum tree', though the local civic association suggests an alternative derivation from the Celtic Pen-lyn-don ("fort at the head of a creek").
By the early 13th century, the river was being called the Plym (Plyme, in 1238), as a back-formation from Plympton and Plymstock (first recorded as Plemestocha in 1086). The earliest records of the name Plymouth date from around this time (as Plymmue in 1230, Plimmuth in 1234).
Plymouth notably lent its name to the settlement of Plymouth, Massachusetts following the departure of the Pilgrim Fathers aboard the Mayflower in 1620, as well as many other settlements in North America.
Read more about this topic: History Of Plymouth