The human heart and soul are so intimately connected that there songs about it. There are also idiomatic phrases about it. People who can’t hide their romantic feelings wear their hearts on their sleeves, and when they experience a change of heart later on, they'll no doubt be brokenhearted unless they saw it coming and hardened their hearts. Needless to say, in such a situation, it’s no wonder if the heart skips a beat, which simply means to become nervous or excited.
English absolutely overflows with idioms. Idioms tend to stick around for a long time, so sometimes, a speaker might know what an idiom means but can’t explain the logic. A good example is the expression “A bird in the hand is worth two in the bush.” This old-fashioned idiom hails from a time in which a falconer was plenty happy to have his or her bird perched on his or her wrist and ready to leap after two unsuspecting partridges hiding in the undergrowth. Others, like the idiom “heart skips a beat,” are more transparent.
One way of explaining why this particular expression is relatively easy to understand is by realizing that the human body has very clear, strong physical and emotional responses to events. Our hearts speed up when we are anxious or excited and especially when we feel the giddy wings of love. A rushing heart seems to trip all over itself, missing a beat then rushing two or three beats together to make up for it. To describe it simply, “heart skips a beat” is an accurate description of what happens physically during the situation.
That means that, when someone says, “My heart skips a beat whenever I think about winning the prize,” an idiom and a description of a physical reaction are simultaneously being expressed. This doesn’t mean, however, that all idioms that take the human heart as their central metaphor will be as easy to understand. Heart idioms that express only physical or emotional reactions will be more comprehensible that those that depend upon objects or attitudes from long ago.
Absence makes the heart grow fonder is something nearly anyone who has spent time away from a much-loved but somewhat annoying sibling can understand; it’s a simple truth disguised as an idiom. When a friend reports that something warmed the cockles of his or her heart, however, the meaning is less clear. A quick trip into linguistics of long ago can help explain this one. Cochleae cordis is Latin for heart ventricles; it was corrupted to cockles as a name for a bivalve sea creature that, when opened, resembles a heart.