It has often troubled me that words sometimes do not mean what they rightfully should. The best example of this, and the one that's bothered me more than any other, is "terrific". Consider:
terrible = horrible
terrify = horrify
terror = horror
terrific != horrific
Turns out, according to dictionary.com, terrific was added to the written English language in 1667 from "terrificus", which meant causing terror. This definition survived for about 140 years. In 1809 the word was given a second meaning: very great, large. I'm all right with that, as it dovetails with the slow evolutions of "enormous" / "enormity", but in 1888 a new usage emerged: excellent.
How did we go from horrible to excellent in 79 years?
I've touched on it, but how did "enormous" go from "very evil" to "very large"? Obviously the two words took the same evolutionary path, albeit in different centuries ("very large" emerged as early as the 1540's).
And, as with "terrific", the old definition is still valid, but often marked Archaic in modern dictionaries.
So what made me think of this? I was walking past the TV this morning when I found myself bored and unsurprised with the "continuing coverage" of the Cleveland shooter. I'm frankly sick to death of the media attention heaped upon these fruit-bats. Anyway, it got me thinking about the expression "going postal" and wondering how many times it took for USPS employees to carve out a little piece of lexicon all for themselves. Turns out (according to wikipedia) there were 40 instances of postal-worker violence from 1986 to 1997, and that the term first entered the language in 1993.
I graduated high school in 1993, and I clearly remember using the expression in high school, so I think it might have been coined in '91 or '92. Maybe it just wasn't used in print, or used frequently enough to get official recognition until 1993.
On a side-note, it's a clear example of the decline in American education when a guy can walk into a school with 2 guns and only manage to wound 4 people before killing himself. Sad, sad, sad.