An amusing thought sir, and it's a real pity that the dictionaries don't make that connection. See my post above for cack-handed, see below for cack:

Cack (?), v. i. [OE. cakken, fr. L. cacare; akin to Gr. , and to OIr. Cacc dung; cf. AS. cac.] To ease the body by stool; to go to stool. Pope.

Both definitions from Webster's 1913 edition via One Look.

Perhaps we should start a dictionary giving definitions and derivations as they would be if life were better arranged. No - come to think of it, that's Hogwash!