(King). A legendary king of Britain, who in his old age divided his kingdom between Goneril and Regan, two of his daughters, who professed great love for him. These two daughters drove the old man mad by their unnatural conduct. (Shakespeare. King Lear.) Percy, in his Reliques of Ancient English Poetry, has a ballad about King Leir and his Three Daughters (series i. book 2).
Camden tells a similar story of Ina, King of the West Saxons (see Remains, p. 306, edition 1674). The story of King Lear is given by Geoffrey of Monmouth in his Chronicles, whence Holinshed transcribed it. Spenser has introduced the same story into his Faërie Queene, book ii. canto 10.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894