A pedigree is a crane’s foot. English took the word in the fifteenth century from Anglo-French pé de grue, after a mark the clerks drew on family charts: one short stroke splitting into three, a parent branching into children, which looked enough like the print a wading bird leaves in mud. Over the centuries the word climbed into the drawing room and came to mean breeding, a long and distinguished line. But the picture inside it was never a line. It was the place where one line stops being one. The word people use to boast of an unbroken descent is named for the mark that showed a family coming apart into more of itself.