Deadnaming is the act of calling a transgender or non-binary person by their birth name or other former forename (their ‘deadname’) after they have chosen a new name. Many transgender people change names as part of gender transition, and wish for their former name to be kept private.

Wikipedia

I just learned about this phrase and had to wonder why it would continue all night. Then I realized the likely hostile holidays with family and my heart sank… I feel so sorry for you. I hope you have someone to lean on. I’d bite the head off of anyone who deadnamed maliciously.