This likely relates to the details of William Tooke’s will. William Tooke, the benefactor of Horne Tooke, died in October 1802. Captain (later Colonel) Harwood, who married Holcroft’s daughter Ann, was Tooke’s nephew. Tooke apparently left Harwood and a great-nephew money on the condition that they took his name.

See David and Christina Bewley, Gentleman radical: a life of John Horne Tooke, 1736–1812 (London: Tauris Academic Studies, 1998), p. 80.