The term "jigsaw" comes from the tool that was originally used to cut the pieces of the puzzle. The tool, called a jigsaw, cuts the pieces in a way that creates irregular edges, making it more challenging to fit the pieces together. The name of the tool was then used to refer to the puzzle itself.
Jigsaw puzzles are cut on the up stroke in order to prevent the wood from splintering. When the blade of the jigsaw is pushed down through the wood, the fibers of the wood are compressed, causing them to splinter and create rough or uneven edges. However, when the blade is pulled up through the wood, the fibers are stretched, creating a smooth and clean cut. This is why jigsaw blades are designed to rotate in an upward motion.
The oldest known jigsaw puzzle is a map of the world created by John Spilsbury in 1767. He mounted a map on a sheet of wood and used a jigsaw to cut it into small pieces. This was a tool used to teach geography to children, but it also became a popular pastime.
Jigsaw is the most common name for this type of puzzle, however, it is also known as a "dissected map" or a "dissected puzzle" in reference to its origins as a tool for teaching geography. Some people also call it a "saw puzzle" or a "picture puzzle" because of the method used to cut the pieces and the final objective of the game.