Chocolate began as a bitter drink in Mesoamerica, made from cacao, often spiced, and not sweetened with sugar. The bar on a modern shelf is a later invention: sugar, milk, and a European sweet tooth rearranged a ceremonial drink into a confection. If the old cup tastes strange to you, that is because you learned the dessert, not the plant.
Worth knowing
Chocolate was a bitter drink long before it was a sweet bar.