Underdark Historical Account
 

One day in the year 3,000 O.R., the world opened up and spit out small people.  The little people claimed to be earth dwellers.  They boasted of a long history underground wherein they had traveled countless miles of caverns and tunnels.  They said that this new world was only one of many their people had found while exploring "Duskkar" (the outlands or, outer world).

The little furry people scurried about the mountains for decades, beyond the limits of what the orcs deemed their empire.  As time passed, two clans of these little people moved out of the mountains and settled in valleys below.  One small group stayed near the mountains while the others settled near the sea.  Those in the foothills were burrowing types - like animals.  They were small, pudgy, and unimposing - about half the size of an orc at best so they were called "Halflings" (yeah, I know it isn't original but work with me here.  Okay?).  The others were tinkers and had named themselves "Gnomes".  Still there was a third group of little people that decided to stay in the mountains and they were called Dwarves.
The Halflings settled for a modest life as sustenance farmers, abiding by a live and let live policy.  They lived in obscurity for years before the orcs came in the year 3,073 O.R.  When approached by the Orc Empire, the Halflings offered tributes to avoid war "what an interesting defense!" thought the orc leaders.  So impressed with the simple wisdom of this non-aggression strategy that they adopted it to their own tactics.  "Why lose good fighters when they are willing to give you the fruits of their labors for free?" they determined.  That action bought the Halflings lasting peace and time rolled on.
By 3, 227 O.R., the Orc Empire was all encompassing.  Orcs threatened to march on the Dwarves and Gnomes unless they started paying tributes too.  To avoid war the dwarven and gnome nations accepted this arrangement and all the nations lived independently in relative peace under the flag of the Orc Empire.