E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
or rather Guanhumara (4 syl.). Daughter of Leodograunce of Camelyard, the most beautiful of women, and wife of King Arthur. She entertained a guilty passion for Sir Launcelot of the Lake, one of the knights of the Round Table, but during the absence of King Arthur in his expedition against Leo, King of the Romans, she married Modred, her husbands nephew, whom he had left in charge of the kingdom. Soon as Arthur heard thereof, he hastened back, Guinever fled from York and took the veil in the nunnery of Julius the Martyr, and Modred set his forces in array at Cambula, in Cornwall. Here a desperate battle was fought, in which Modred was slain and Arthur mortally wounded. Guinever is generally called the grey-eyed; she was buried at Meigle, in Strathmore, and her name has become the synonym of a wanton or adulteress. (Geoffrey: Brit. Hist., x. 13.)
That was a woman when Queen Guinever of Britain was a little wench.Shakespeare: Loves Labours Lost, iv. 1.