The English word chocolate comes via Spanish from the Nahuatl word, xocolatl, which means 'bitter water'. The words for chocolate in most other languages come from the same root, either directly, or via other languages such as English.
The ancient peoples of Central and South America used cacao as a food, a drink and even a currency. They prepared the drink by fermenting, roasting and grinding up cacao seeds and making them into a paste which they mixed with chilies, cornmeal and other ingredients. Among the Maya, most people could drink this special beverage, but the Aztecs saw it as a sacred drink and only permitted rulers, priests, decorated soldiers, and honored merchants to partake of it. Sauces made from bitter cacao and chilies remain popular in Mexico, where they are used to accompany meat.
When the Spanish arrived in Mexico in the 16th century they recognised that cocao was valuable and started sending it back to Spain. They began to make cacao drinks with cinnamon, other spices and sugar, and eventually the rest of Europe started drinking chocolate as well, although for it remained the drink of the elite for several centuries due to the high cost of the ingredients.
By the 18th century it was possible to mass-produce chocolate bars and other cacao-based sweets cheaply and they became available to everyone.