Cielgender is a xenogender that is connected to all aspects of the sky.
This term was coined by Reddit user SixSaltines in a now-deleted Reddit post on an unknown date.
An archived version of the post can be found here 
The flag was coined alongside the term, on the same date.
The black represents the midnight sky, the purple represents the dusk sky, light purple represents the dawn sky, blue represents a clear sky, pink, yellow and orange represent sunrises/sunsets, and the stars.