Hand over fist

The first source I looked at claims it is of naval origin and refers to the pulling in of ropes, or climbing ropes. I'm not convinced. But it does say this - which sounds better:

"The 'making money hand over fist' figurative use is a clear allusion to grabbing handfuls of money and pocketing it. This is later, but not much later, in Seba Smith's The life and writings of Major Jack Downing, 1833:

"They... clawed the money off of his table, hand over fist."

Now that's clear imagery.