Fear not, dear readers. Our research department found the following:
The term originated in 1889 when the U.S. government opened Oklahoma, then an Indian territory, to expansionists who were salivating over the term 'manifest destiny.' To claim their land, several expansionists participated in a land run, not unlike the beginning of the childhood game "Ghost in the Graveyard."
Turns out that some of the settlers got a head start on the whole shebang, and they were dubbed "sooners" by their jealous, law-abiding counterparts.
Here's how Dictionary.com defines the word 'sooner':
1. a person who settles on government land before it is legally opened to settlers in order to gain the choice of location.
2. a person who gains an unfair advantage by getting ahead of others.
For you film buffs out there, the event served as the backdrop for the 1992 Tom Cruise/Nicole Kidman epic "Far and Away."
Here's the entirely unreliable Wikipedia page on sooners.
And here's the Ask Yahoo page.
Now you know. And ...