Making money hand over fist is an idiom that dates back to early sailors. They would pull in their catches using a "hand over fist" method to reel the traps or lines in from the ocean. This meant that money (in the form of fish or crabs) was coming to the boat hand over fist.

Probably a nautical term used when hauling a rope, originally quoted as 'hand over hand'

There is the over-hand serve and the under-handserve. The over-hand is when you hit the volleyball with your palm or fist over your head. The under-hand is when you hit the volleyball with your palm or fist under your head. The point of both of the serves are to get the ball over the net and in between the out lines.

Below a fist of a hand are the fingers, palm, and wrist.

I believe you mean "hand over fist." It means that money and merchandise are being exchanged very rapidly.