Tumblrgender is a xenogender related to Tumblr. One who is Tumblrgender feels as if their gender is closely connected to the social media site Tumblr. It can also be used as a reclaimed term, coined for people who are frequently assumed to be faking being transgender for attention. This definition is closely related to gender nonconforming trans people, xenic people, people who use neopronouns, etc.
History
The term first appeared around a similar term, trendergender, meaning that someone was 'pretending' to be transgender, usually due to having a xenogender, using neopronouns, being gender nonconforming, etc. It came from a lot of these concepts being extremely popular on Tumblr.
On April 10th, 2021, tumblr user incusins made a post coining two new definitions for Tumblrgender, including two new flags they made for the term.[1]