The heart shape is an ideograph used to express the idea of the “heart” in its metaphorical or symbolic sense as the center of emotion, including affection and love, especially romantic love. The “wounded heart” indicating lovesickness came to be depicted as a heart symbol pierced with an arrow (Cupid’s), or heart symbol “broken” in two or more pieces.
The combination of the heart shape and its use within the heart metaphor developed at the end of the Middle Ages, although the shape has been used in many ancient epigraphy monuments and texts. With possible early examples or direct predecessors in the 13th to 14th century, the familiar symbol of the heart represented love developed in the 15th century, and became popular in Europe during the 16th.
Before the 14th century, the heart shape was not associated with the meaning of the heart metaphor.