I heard that one as a youngster from a plumber who was rodding the drain in my parent's basement - circa 1986 or so.

He used to connect all his plugs, and operate all his switches "backhanded", under the belief that, if your arm muscles involuntarily contract with your palm towards you, they would pull back towards the center of the body, rather than pressing the hand against the energized surface, as would supposedly happen with the palm away from you.

In the fire service, we check doors for heat using the back of our hands for three reasons - first, because the back of the hand is more sensitve to heat/cold (less callouses, scars, etc; secondly because the pain generated by a really hot door will cause you to flinch, and your arm seems to pull away faster palm-in; and third, because you can still use your hand to write / drive / grasp stuff if the back of it is burned checking a "too hot" door for heat! [Linked Image]