Trendergender is a xenogender which reclaims the word "transtrender." It was coined for people who are assumed to be faking being transgender for attention. It's associated with gender nonconforming trans people, non-dysphoric trans people, xenic people, people who use neopronouns, etc.
The trendergender flag was created by @beanieworm on Twitter. It is unknown when it was created. The stripes, in order, represent acceptance, MOGAI, gender nonconforming trans people, non-binary people, neopronouns, xenogenders, and love. The alternate flag was made by FANDOM user DentalFricative, with the same meaning, just lighter colors.