I think the term freeze plugs may have come about when someone had an engine to freeze up and when the water froze it expanded and pushed out a "weak" plug.
I personally have seen this happen on my granddads old truck. I suppose the plug was so weak and rusted that when the water froze it pushed it out.
Back in the "old days" I have seen my grandparents actually lay a heavy quilt over the front of the grilles to help keep out the cold. He said he couldn't afford but one quart of antifreeze and the quilt helped. I can still see him doing that in the mid 50"s.
