It comes from "Trojan horse", which is disguised as something harmless and then starts to cause damage after getting inside.
Trojan, also known as Trojan virus, refers to controlling another computer through a specific program (Trojan program). Trojans usually have two executable programs: one is the control end and the other is the controlled end. The name Trojan horse comes from ancient Greek legend (the story of the Trojan horse trick in Homer's epic poem, the word Trojan originally means Trojan, which refers to the Trojan horse, that is, the story of the Trojan horse trick). "Trojan horse" program is a relatively popular virus file at present. Unlike ordinary viruses, it does not reproduce itself, nor does it "deliberately" infect other files. It disguises itself to attract users to download and execute it, so as to seed Trojan horses. The attacker provides a portal to open the planted host, allowing the seeder to destroy and steal the planted host's files at will, and even remotely control the planted host.