While it sounds like a type of fabric, a calico toile is actually a tool used by a dressmaker when making a handmade garment.
A toile is a mock-up of a dress or other garment that a dressmaker makes to ensure proper fit before constructing the garment out of the intended fabric.
Toiles are typically made out of a calico material since calico is fairly inexpensive. A toile would not be made out of a pricey fabric because it will never be worn and would therefore be a waste of the fabric.
How It's Made
A calico toile is a mock-up of a custom made garment. The dressmaker makes a replica of the garment out of scrap fabric and fits it to the customer. This mock-up is then fitted to the customer to ensure an exact fit.
First the dressmaker creates a custom pattern for the garment. The calico toile is created from this pattern.
The toile is fitted to the customer and then used to as a new pattern with the custom measurements. The pattern made from the toile is then used to create the final garment out of the selected fabric.