According to the Farmers' Almanac:
The fishing tribes are given credit for the naming of this Moon, since sturgeon,
a large fish of the Great Lakes and other major bodies of water, were most readily caught during this month. A few tribes knew it as the Full Red Moon because, as the Moon rises, it appears reddish through any sultry haze. It was also called the Green Corn Moon or Grain Moon.
Dakota Sioux called this the 'Moon When All Things Ripen'
Cherokee called it 'Fruit Moon'
Chocktaw named it 'Woman's Moon'
to the Medieval English it was known, 'Corn Moon'