1) A polite way of saying cock slap. Often results in a mushroom tattoo if done properly. If not done probably often just ends up in an angry person. Reasons for this include the recipient showing a complete lack of respect towards the giver, a show of male (or female in strange circumstances) dominance and also the most popular seems to be just for a bit of fun. Often uses a left to right motion and in extreme circumstance of severe lack of respect the giver is allowed to add a right to left motion therefore resulting in a mushroom tattoo on each side of the recipients face.
2) A royal English way of saying a handjob.

When you eat dirt for the first time and leave your family to build a shack in the woods