Green’s Dictionary of Slang

to be of no consequence, to not matter at all.

1913		A. Lunn Harrovians 87: It don’t matter a twopenny damn if they score again.
1938		G. Kersh Night and the City 249: Chisel, chisel, chisel, without a tuppeny damn’s worth of thought to your credit.
1946		B. Charles 22 Jan. diary in Garfield Our Hidden Lives (2004) 170: They dissipate all their energies on utterly piffling things, things that don’t matter a tuppeny damn.
1958		(con. 1940s) B. Behan Borstal Boy 313: Won’t matter a tuppenny.
1964		T. Ronan Packhorse and Pearling Boat 123: ‘Were you scared, Dad?’ ‘Didn’t matter a tuppenny damn whether I was or whether I wasn’t.’.
2001		M. Walters Dark Room 287: It wouldn’t matter a tuppenny damn what I’d done if either Miles or Fergus could stand up and be counted.