Uncle Toby and the fly

Uncle Toby Shandy, Tristram says, had “scarce a heart to retaliate upon a fly.” A ten-year-old Tristram sees this scene:


Laurence Sterne, The Life and Opinions of Tristram Shandy, Gentleman 2.12 (1759).

Though Tristram gives some credit to “the study of the Literae humaniores, at the university,” he tells us that he believes he owes half of his philanthropy “to that one accidental impression” made upon him by his uncle.

Also from Sterne
Letters for all occasions : Yorick, distracted : Yorick, translating : Yorick, soulful : Digressions

[The American Heritage Dictionary of Idioms (1997) dates not hurt a fly to the early 1800s. Does Uncle Toby lurk quietly in the idiom’s backstory?]