On the basis the street running parallel, Camden Street was called after the Earl of Camden (John J Marshall, Belfast Telegraph, 03/01/1941) the editor believes Fitzwilliam Street was then called after William Fitzwilliam, 4th Earl Fitzwilliam who was Lord Lieutenant in Ireland from 13 December 1794 – 13 March 1795. The street is featured in the 1852 edition of Henderson’s Belfast Street Directory with a few houses.