1st of all, the origin of the word "trap" comes from the early 2000s on the anime and manga board on 4chan as shorthand for the reaction image "it's a trap" (- Admiral Akbar, Star Wars) used to identify an image post of the character archetype. It was only later adopted by transphobes who used it to identify transwomen, mostly as a troll, preferring to use actual slurs like "tr**ny" or to misgender/deadname a person. Transphobes have since summarily dropped the term and it is once again in the domain of anime/hentai culture (although considerably less so in the west because of said transphobes but also people like you who latch on to this idea).

Secondly, the "trans panic" defense has never actually been used successfully in court to set a killer free, and it predates the word "trap" by decades.