October is the Hunters moon. Second moon of any month is called a blue moon.
Based on a mistaken interpretation of the Old Maine Almanac in Sky and Telescope Magazine in March 1946, a mistake that became canonical when propagated by the game Trivial Pursuit. The original Maine Almanac definition was the third full moon in an astronomical season containing four. The third, because then the other moons would have the proper relation to the cardinal points of the sun, for instance last full moon before the winter solstice was the Yule moon.
In 19 years there are almost exactly 235 lunations, but only 228 calendar months, and 76 seasons. Therefore there must be at least seven months with two full moons and seven seasons with four full moons. There can be more than seven such months in 19 years, because when there are two full moons in January, there may be none in February and two again in March of the same year. That happened in 1999 and again in 2018, and will again in 2037.