Original: Perhaps the most cited explanation is that "chocolate" comes from Nahuatl, the language of the Aztecs, from the word "chocolatl", which many sources derived from the Nahuatl word "xocolatl" made up from the words "xococ" meaning sour or bitter, and "atl" meaning water or drink.
Simplified: The word for "chocolate" in almost every language comes from its name in the Nahuatl language of Mexico, chocolatl.