The story
From mal- + gender. First known use is by Tumblr blogger penisbagelbite in the April 2024 blog post " 'Affirmation' & Malgendering".
Etymology from Wiktionary, CC BY-SA 4.0.
malgender
Today it means: To insincerely or disparagingly gender an individual correctly, particularly to do so by referencing gender stereotypes (e.g. telling a trans man he is archetypically unhygienic). Full definition →