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 restraint, and the abbeys dissolved and their riches shared out. King Henry, forewarned of their intention by a spy, moved to London, and when the Lollards assembled in force in St Giles's Fields on 10 January they were easily dispersed by the king and his forces. Oldcastle himself escaped into deepest northwest Herefordshire, and for nearly four years avoided capture. Apparently he was privy to the Southampton Plot in July 1415, when he stirred some movement in the Welsh Marches. On the failure of the scheme he went again into hiding. Oldcastle was no doubt the instigator of the abortive