Murphy's law is an adage or epigram that is typically stated as: "Anything that can go wrong will go wrong".
The British stage magician Nevil Maskelyne wrote in 1908:
It is an experience common to all men to find that, on any special occasion, such as the production of a magical effect for the first time in public, everything that can go wrong will go wrong. Whether we must attribute this to the malignity of matter or to the total depravity of inanimate things, whether the exciting cause is hurry, worry, or what not, the fact remains.
Maskelyne was a public detractor of Guglielmo Marconi in the early days of radio (wireless). In 1903 he hacked into Marconi's demonstration of wireless telegraphy, and broadcast his own message, hoping to make Marconi's claims of "secure and private communication" appear foolish.
The threat of backdoors surfaced when multiuser and networked operating systems became widely adopted. Petersen and Turn discussed computer subversion in a paper published in the proceedings of the 1967 AFIPS Conference.
They noted a class of active infiltration attacks that use "trapdoor" entry points into the system to bypass security facilities and permit direct access to data. The use of the word trapdoor here clearly coincides with more recent definitions of a backdoor. However, since the advent of public key cryptography the term trapdoor has acquired a different meaning (see trapdoor function), and thus the term "backdoor" is now preferred.