Nation sack is actually Notion sack or a corruption of notion sack. Whenever times are good (financially) you stick a little bit back in your "notion sack". That way if you take a notion to do something or go somewhere you have the money to do it. Notion is a very popular word in the Southeastern US. People say it all the time. "When I take a notion to leave they better watch out.", "It was so hot the other day I took a notion to go to the lake for a swim." "I was sitting there and the notion stuck me to knock the crap out of him.(I was sitting there and the idea came to me to hit him really hard.)" there are some examples. Notion is basically another word for idea but it is an idea that is normally acted on. An idea that you want to act on I guess I should say whether or actually should or not.