I have been watching some of the old "Hollywood Squares" shows, and they had "Dame Edna" on as the center square. I remember this character appearing on various shows in the '80s and '90s. I thought, "Was this an early trannie advocate?". So I looked him up. The character was played by a comic from Australia named Barry Humphries. He first started the character in 1955! Turns out he was far from being a trannie, but apparently crosse the line in 2018:
In 2018, Humphries was criticised on social media for making comments considered by some to be transphobic.[108] The comments included referring to gender affirmation surgery as "self-mutilation" and transgender identity as a whole as a "fashion—how many different kinds of lavatory can you have?" The comments prompted the Barry Award, a comedy festival award in Melbourne named after the comedian, to be renamed the Melbourne International Comedy Festival Award the next year.[109] (from wikipedia, so sue me)
He died this year, but is not included with the "celebrity death" list USA Today keeps, which includes MANY people I have never heard of. Just shows that if you don't tow the line (or is it "toe the line") in show business, you won't be counted as a celebrity when you die. Of all the groups in the world who shouldn't care what someone thinks about something, pretty sad that a comedy festival showed their full wokeness by changing the name of an award because he showed signs of being "transphobic".
You are correct. The term was used in boxing to start the fight both boxers had to get right up to a line in the dirt and face each other to start the match.