When you have a party and someone you invited (the governmenter) brings an entourage that outnumbers the total number of people you originally invited. This often results in the taking over of your party or the proverbial "stealing of one's thunder".
Originated because government representatives will always outnumber a company's representatives at any meeting.
"Why are all these people at my party? I didn't invite them..."
"They all came with (name of governmenter)."
"That's more people than I invited to my own party!"
"You've just been governmented."