'To know something like the back of your hand.' I have looked in many reference books but have never found a plausible explanation of this phrase. Since I doubt that most people would actually be able to identify a picture of their own hand from a selection of the same I think we may have to think outside the box to get a handle on the origin of this saying. Any suggestions?
Sunk: he says: " I have looked in many reference books but have never found a plausible explanation of this phrase." - well the explanation is obvious. I know what the back of my hand looks like very well.
Perhaps...
People write cheats, prompts, lines on the back of their hands. Maybe it is a self effacing comment meaning I am bluffing my knowledge a bit.
Here is my take on this saying. The 'hand' is the hand that you are dealt with in a poker game. You look at it, carefully remembering the cards. Then you might place the cards face down on the table. Your 'hand' is now not visible to anyone. The 'back of your hand', face down on the table, is known only to you. That is the explanation and origin of the phrase.