Some think the heart-shape is a stylised depiction of human anatomy, representing the curved shape of breasts or buttocks. Others suppose it’s inspired by ancient philosophers, who believed the heart was the seat of the soul and the emotional centre. While physicians such as Galen, the 2nd century father of medicine, described the heart as a three-chambered organ shaped like a pine cone.
Over time, heart-shapes remained popular in decorative art and heraldry, but did not gain a strong connection with love until 13th century. The Medieval concept of courtly love led to more illustrations glorifying romance, often using the heart-shape as a symbol for love, as in the 1250’s French manuscript the Roman de la poire, in which a young man holds his vaguely pine cone-shaped heart up towards his lady love. Up until 14th century, the heart was usually depicted upside down. This shifted in 15th century, as the heart symbol came to resemble what we use today, and became a suit on playing cards.