Aciengender is a xenogender that feels like it came from a different time period. For example, a boy who feels like his gender came from the 1920s, or a non-binary person who feels like their gender was from the Victorian era. Aciengender is not "My gender is the 1940s" rather "My gender feels like it came from the 1940s".
Aciengender was coined on February 1st, 2021 by a user going by Shy to describe some of his experiences with gender. The flag was also coined by him on the same day.
The term originated from the French word "Acien" meaning "vintage"