chocolate n.

c. 1600, from Mexican Spanish chocolate, from Nahuatl (Aztecan) chocola-tl,"chocolate," and/or cacahua-tl "chocolate, chocolate bean." With a-tl "water." In the first form, the first element might be related to xocalia "to make something bitter or sour" [Karttunen]. Made with cold water by the Aztecs, with hot water by the Conquistadors, and the European forms of the word might have been influenced by Mayan chocol "hot." Brought to Spain by 1520, from there it spread to the rest of Europe. Originally a drink made by dissolving chocolate in milk or water, it was very popular 17c.

To a Coffee-house, to drink jocolatte, very good [Pepys, diary, Nov. 24, 1664].

As a paste or cake made of ground, roasted, sweetened cacao seeds, 1640s. As "a piece of chocolate candy," 1880s. As a dark reddish-brown color from 1776. The adjective is from 1723 as "made of or flavored with chocolate;" 1771 as "having the color of chocolate." Chocolate milk is by 1845.  Chocolate-chip is from 1940.