“Worm grunting, also known as worm fiddling or charming, involves driving a wooden stake into the ground and rubbing the top of it with a leaf spring or other flat piece of steel to make a grunting or snoring noise. Done in the right place under the right conditions, the result will be hundreds earthworms appearing on the surface of the ground. Worm grunting is practiced in parts of the southeast to obtain fish bait.�?
Vanderbilt.edu: 'Worm grunting involves going into the forest, driving a wooden stake into the ground and then rubbing the top of the stake with a long piece of steel called a rooping iron. This makes a peculiar grunting sound that drives nearby earthworms to the surface where they can be easily collected for fish bait.
'Despite a lot of speculation, worm grunters don't really know why the technique works.'