Shadend

Shadend is an aesthetigender in which one feels as though one’s gender is, or is connected to shadows or darkness in some way; up for interpretation.

Similar terms include: murkend

History & Flag
It was coined on August 10, 2019 by Tumblr user wavership. Wavership is also the creator of the flag, which they coined with the term on the same date. The colours likely represent shadows.