heartstring

Before a song or movie or heart-shaped card accompanied by a box of chocolates could tug at your heartstrings, the job was more likely to be accomplished by a surgeon: the word heartstring used to refer to a nerve believed to sustain the heart. You might recognize the word's second syllable in the term "hamstring," which refers to both a group of tendons at the back of the knee and to any of three muscles at the backs of the upper legs. It's also apparent in a rare dialect term for the Achilles' tendon: "heel string." And in light of these terms, it's not surprising to know that "string" itself was at one time used independently to refer to cords like tendons and ligaments.