Short answers, pulled from the story.
Cacao was first domesticated at least 5,300 years ago by the Mayo-Chinchipe culture in what is now Ecuador, with cacao beverages consumed by the Maya 2,500-3,000 years ago. A chocolate drink was an essential part of Aztec culture by 1400 AD.
Among the Aztecs, chocolate was a sign of high status, and it was considered a bad omen for anyone of low or common rank to drink it. Cacao beans also circulated as currency throughout Mesoamerica.
Sir Hans Sloane, president of the Royal College of Physicians, encountered cocoa in Jamaica in the late 17th century and found it nauseous until he mixed it with milk. He brought that recipe back to England, introducing milk chocolate to the country.
Hot cocoa is made from cocoa powder, which has had much of its cocoa butter removed, while hot chocolate is made directly from bar chocolate that still contains cocoa butter, cocoa, and sugar. This missing cocoa butter makes hot cocoa significantly lower in fat while it still carries chocolate's antioxidants.
Italy serves a thick version called cioccolata calda, Spain has chocolate a la taza, and the United States favors a much thinner cocoa, often instant. Distinctive local touches include farmer's cheese in Colombia and Ecuador, an egg yolk in the Viennese variant, and muscovado sugar in the Philippines' tsokolate.
Hot chocolate reached North America as early as the 17th century, brought by the Dutch, but colonists did not begin selling it commercially until around 1755. It has since become associated with cold weather and winter in the United States and Canada.