Just for your info, wikipedia theorizes that the etymology of the above phrase is as follows:
It is unclear exactly how this expression came to be, but the consensus is that it is based on Native Americans having a distinctly different sense of property ownership as opposed to those of European ancestry. One theory holds that early European settlers in North America misinterpreted aid and goods they received from Native Americans as “gifts,” when in fact they were intended to be offered in trade, as many tribes operated economically by some form of barter system, or a gift economy where reciprocal giving was practiced. It is also theorized that this stereotype may have been coined or exaggerated by the conquering European groups to denigrate the native people as dishonest and thereby justify their conquest. A popular myth started by Europeans tells of early settlers trading firearms to a group of Native Americans for maize, who then promptly turned the guns on the Europeans and reclaimed their crop.
Just something to think about the next time you use or hear that phrase.