Asiergender is a gender tied to age regression. When one in a regressed state, they identify as their AGAB. Specifically, however, they only identify with the diminutive form of it - as a girl or boy rather than a woman or man, because the latter forms are perceived to be too "grown-up" or "adult" for the individual while they are in a regressed state. This is similar to and may be considered a subset of pleonotic. It may also be considered an agregender, ageregender, and/or littlefluid identity.
The term was coined on June 20th, 2021 by Tumblr blog mygenderisamess. The flag was released in the same post.