1610s, "unconcerned," the sense we now would ascribe to uninterested, with the sense of "impartial" going to disinteressed (c. 1600). See dis- + interest. Modern sense of disinterested is first attested 1650s. As things now stand, disinterested means "free from personal bias," while uninterested means "caring nothing for the matter in question." Related: Disinterestedly; disinterestedness.
1. The current sole superpower is far from being a disinterested observer.
2. Lili had clearly regained her appetite but Doran was disinterested in food.
3. Such benevolence, however, was not completely disinterested.
4. We had both become jaded, disinterested, and disillusioned.