Some historians suggest a darker origin. During the dry, windy conditions of late autumn, the risk of forest fires was high. These fires were often started by Native Americans clearing land for hunting or signaling, creating a smoky haze in the air. Thus, the term referred to the specific atmospheric conditions created by these fires.
The origins of the term are debated, but it dates back to at least the late 1700s in North America. There are three leading theories on how the name came to be: whats an indian summer
In modern usage, an Indian Summer is a period of unseasonably warm, dry weather that occurs during autumn, specifically after the first killing frost of the season. Some historians suggest a darker origin