For the plot of his play in verse “Zapolya, A Christmas Tale in two parts” (1817), S. T. Coleridge made use of some incidents from the history of Croatia and Hungary that took place immediately after ...the death of king John Zapolya (1487-1540). The heroine of Coleridge's play is obviously king John's widow, Zapolya, Queen of Illyria. He calls her simply Zapolya, although her real first name was Isabella.
In the “Advertisement” to his play Coleridge says: “The form of the following dramatic poem is in humble imitation of The Winter's Tale of Shakespeare.” And although he further says that his debt to Shakespeare is “a matter of form merely”, the story of the “Old Mountaineer” Bathory, who brings up the young prince Andreas as his own son in “a cavern overhung with ivy”, was obviously suggested to him by Shakespeare's story of Perdita who is raised by an “Old Shepherd” as his daughter.
It is just possible that another play of Shakespeare, his 'Twelfth Night' of which the action is set in Illyria, prompted Coleridge to write his play about an Illyrian queen.