Not all of the miners stayed for the winter. Those who moved south to Illinois came to be known as suckers, after a migratory freshwater fish, a name that came to be applied to all Illinoisans. And that was not an insult--one of Illinois' nicknames is The Sucker State.
Same fish, different story in east central Illinois: The “Suckers” were people from Indiana who came to Illinois to vote and then returned to Indiana.