The lake has been named after the legend of King Lear (Leir), who possibly ruled Britain in the 8th century. On his death it is said that his daughter Cordelia had him buried in a chamber under the River Soar. There are statues, built on a platform in the lake, showing the final scene from Shakespeare's play of King Lear.
Historian's are mixed on the existence of a warrior king called Leir. Geoffrey of Monmouth in the 12th Centruy (who has been so often discredited) describes him as a pre- Christian warrior king whose greatest achievement was that he “built, upon the river Sore(Soar) a city, called in the British tongue Kaerleir, or in the Saxon, Leircestre”...but it is now thought he may have taken the story of the existence of this king from an earlier myth.
Leicester as a settlement far pre-dates this but after the Roman withdrawal from Britain it fell into decline. This Was Leicestershire has a good article about more contemporary views of Leir which offer a different explanation of the local associations with the name and links to the worship of an important water god in this locality.
Drawing: Paul Gent for Charnwood Arts' Heart of Three Cities newspaper.