Pyrogender is a naturogender that is connected to fire. It holds a stronger aesthetic connection with fire than firegender does. It is not just connected to the movement of the fire but the heat of the fire and the consumption of fuel to keep it burning, like it is eating up other genders to keep the main one going in a way (this may not apply to every pyrogender individual). The main thing is feeling like one's gender is a fire, and feeling something about it.
The term was coined on Febuary 22, 2017 by an anonymous submitter on ask-pride-color-schemes's tumblr. The flag was created at the same time.