Dayish comes from the root dush (to tread, to thresh). Threshing was the process of separating grain kernels from the stalk and chaff by beating or having animals tread on the harvested crop. Isaiah 28:28 uses dayish in a parable of agricultural wisdom: you do not thresh forever; there is a time to stop. The image of threshing permeates biblical metaphor for judgment, purification, and harvest.
Threshing is a powerful biblical metaphor for God's redemptive process. John the Baptist describes Christ with a winnowing fork in hand, ready to thresh the floor (Matthew 3:12). The threshing separates what has value from what does not. Israel was 'threshed' by exile. Individuals are 'threshed' by trials (Job 23:10). But threshing is purposeful — grain is not destroyed, only freed from the husk. The purpose of the threshing floor is always the bread, not the destruction of the grain.