Firejack means "blanch". The word "blanch" is actually a portmanteau of "fuck".

"Blanch" and "Gotham Nightmare" are both stems that originally came from an uploader named "Gotham Nightmare Heran". Every single video the uploader posted was shouting out a corny line, complete with an abstract imitation of the Joker's makeup and a hilariously tight fall suit, giving a huge contrast to the Joker's role as Gotham City's in the movie.

So many netizens who saw his Joker cosplay called out "Gotham has a nightmare". So, this is also the origin of the "Gotham nightmare" terrain. The term is often used to describe embarrassing scenes or events.

Source:

"Blanch" is pronounced as "chao", which generally means to blanch ingredients in hot water, such as blanching spinach, blanching ribs, etc. The word "blanch" is also used to describe an embarrassing scene or an embarrassing event.

In Internet parlance, blanching is actually the harmonious terrain of "#" (cao), which comes from the video author @GothamNightmare, who makes earthy cross-dressing videos. I'm not easy to heart once, but you let me lose so completely after making a cup slamming action and shouting a "#" after the cross-dressing clown, after which the "#" was harmonized into "blanch".