Flapping
Flapping is a repetitive up-and-down motion most commonly associated with a bird's wing in flight. Birds flap to provide airflow against their wing, thereby generating lift. Larger wings are more efficient (a side-effect of their aspect ratio) so smaller birds must flap much more quickly, while larger birds can soar without flapping for long periods. It is thought that this word may be an example of onomatopoeia.
The term flapper refers to a young fledgling, a bird "testing its wings" before physically able to fly. However the term is more commonly associated with the slang term from the period after World War I to refer to young women, based on the same etymology.
