The Merry Wives of Windsor in 1597, after which controversy over the original naming of Falstaff (he was originally the historic Sir John Oldcastle, which presumably did not please Oldcastle's descendants) forced Shakespeare to rename the character. It appears that the joke in V,v,85–90 is that Oldcastle/Falstaff incriminates himself by calling out the first letter of his name, "O, O, O!," when his fingertips are singed with candles—which of course works for "Oldcastle" but not "Falstaff." There is also the "castle" reference in IV,v,6. 18 January 1602 was the date the play was entered into the Register of the Stationers Company. The first quarto was
John Oldcastle in the parliament of 1404, later serving as a justice of the peace, and was High Sheriff of Herefordshire in 1406–07. In 1408 he married Joan, the heiress of Cobham — his third marriage, and her fourth. This resulted in a significant improvement of his fortune and status, as the Cobhams were "one of the most notable families of Kent". The marriage brought Oldcastle a number of manors in Kent, Norfolk, Northamptonshire and Wiltshire, as well as Cooling Castle, and from 1409 until his accusation in 1413 he was summoned to parliament as Lord Cobham. At some point in his