seed from which cocoa and chocolate are made, 1550s, from Spanish cacao "the cocoa bean," an adaptation of Nahuatl (Aztecan) cacaua, root form of cacahuatl "bean of the cocoa-tree."
Entries linking to cacao
cocoa n.
"brown powder produced by grinding roasted seeds of the cacao, an American evergreen tree," 1788, originally the seeds themselves (1707), corruption (by influence of coco) of cacao. The confusion with coco was already underway in English when the printers of Johnson's dictionary ran together the entries for coco and cocoa, after which it has never been undone. Cocoa has been the regular spelling from c. 1800.