peräin
Peräin is a Finnish term that can refer to several things, primarily related to boats and vehicles, and also to a specific geographical location. In nautical contexts, peräin refers to the rudder, the steering device used to control the direction of a boat or ship. It is typically a flat piece of wood or metal attached to the stern, and its movement changes the flow of water, thus altering the vessel's course.
The term can also be used more broadly in some technical contexts to describe a rear part