Today, piping hot usually means comfortably warm food straight from your own oven to the table, but it took a few centuries to evolve into that meaning.
There was a time when everyone bought freshly baked bread every day from a neighborhood or village baker.
When the bread was ready, the baker would signal from his front door by blowing on a pipe or horn.
This caused people to hurry to get bread before it ran out and gave us the expression “piping hot” for yummy warm food.