Daughter of Lord Robert Fitzwalter. Michael Drayton has a poem of some 670 lines so called.
Daughter of Rokeby, and niece of Mortham. She was beloved by Wilfrid, son of Oswald, but loved Redmond, her father's page, who turns out to be Mortham's son. (Scott:
Sister of Gessler; in love with Arnold, a Swiss, who had saved her life when threatened by the fall of an avalanche. After the death of Gessler, who was shot by William Tell, the marriage of these lovers is consummated. (Rossini: Guglielmo Tell
, an opera.)
Gifford's Baviad and Mæviad
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894