Know like the back of one’s hand

One would imagine that we really know the back of our own hands very well, considering that our hands are in front of us all the time. Thus, the meaning of the expression is not in the least surprising. The surprise, however, is that the expression only came into popular usage during the 19th century with its first appearance in print in Robert Louis Stevenson’s Catriona (1893), “I should ken this country like the back of my hand.” It is curious that the backs of our hands, staring us in the face through the centuries, should only materialise as a common everyday expression as late as the 19th century.