The double-lobed heart icon -the Valentine shape- existed as an iconic shape before it was associated with the blood pump inside us. It may have come from the shape of a butt, or testicles, or the silphium plant, or any number of other inspirations. That was a long time before it was associated with the physical heart, or with love.
“[The heart] might’ve also been the brand for horses,” says Yalom, “Why not? The double lobes do suggest haunches.” Were they symbols of war? Strength? All the wine they would drink after battle? Who knows. But in the Middle Ages, the real fun begins. This was the age of courtly love. Medieval philosophers looked to Aristotle, who said that sentiment lived not in the brain but the heart, for cues on where to pinpoint thine #feels. In Medieval Bodies: Life, Death and Art in the Middle Ages, Josh Hartnell explains that they also inherited the Greek idea that the heart was the first organ your body made, and hence, the one that most anchored your human existence – it was the “house of the human soul.”
It took a long time for the physical heart, the heart icon, and the concept of romantic love to come together. How it happened is a story you can read at Messy Nessy Chic.