Wait, "Hot" could be a keyword here. Maybe it's related to the color red in Mizo culture, which is important in rituals. Thawnthu is part of traditional dress where women wear a puanpial (shawl) with Thawnthu, which is red. So combining all these: Mizo culture, the Puitling festival involving Thawnthu attire, maybe the red color is significant.
