Green’s Dictionary of Slang

for the sake of.

1958		F. Norman in Sun. Graphic 20 July in Norman’s London (1969) 19: I went up to him and bought one down to the old pals act.
1962		R. Cook Crust on its Uppers 20: I’ve done some odd things but all down to learning.
1995		J. Cameron Vinnie Got Blown Away 130: He cottoned what it was down to.