The etymology of King’s Lynn is uncertain. The name Lynn may signify a body of water near the town – the Welsh word llyn means a lake; but the name is plausibly of Anglo-Saxon origin, from lean meaning a tenure in fee or farm. As the 1086 Domesday Book mentions saltings at Lena (Lynn), an area of partitioned pools may have existed there at the time. Other places with Lynn in the name include Dublin, Ireland, with An Dubh Linn meaning “the Black Pool.” The presence of salt, which was relatively rare and expensive in the early medieval period, may have added to the interest of Herbert de Losinga and other prominent Normans in the modest parish.

The town was named Len Episcopi (Bishop’s Lynn) while under the temporal and spiritual jurisdiction of the Bishop of Norwich, but in the reign of Henry VIII it was surrendered to the crown and took the name Lenne Regis or King’s Lynn. The Domesday Book records it as Lun and Lenn, and ascribes it to the Bishop of Elmham and the Archbishop of Canterbury.

The town is generally known locally as Lynn.

The city of Lynn, Massachusetts, north of Boston, was named in 1637 in honour of its first official minister of religion, Reverend Samuel Whiting Sr, who arrived there from Lynn, Norfolk.