Edward A. Murphy, Jr. was one of the engineers on the rocket-sled experiments that were done by the United States Air Force in 1949 to test human acceleration tolerances (USAF project MX981). 

One experiment involved a set of 16 accelerometers mounted to different parts of the subject's body. There were two ways each sensor could be glued to its mount. Of course, somebody managed to install all 16 the wrong way around. 

Murphy then made the original form of his pronouncement, which the test subject (Major John Paul Stapp) quoted at a news conference a few days later. 

Within months, "Murphy's Law" had spread to various technical cultures connected to aerospace engineering, and finally reached the Webster's dictionary in 1958. 

When some of us old timers need a place to lay the blame for things go wrong, we often say that "Murphy" has been following us around all day.  Sorry, Edward.  No personal offense intended.