In social situations, a wallflower is a shy or unpopular individual who doesn't socialize or participate in activities at social events. He or she may have other talents but usually does not express them in the presence of other individuals. The term comes from the image of a person isolating themselves from areas of social activities at ballroomdances and parties, where the people who did not wish to dance (or had no partner) remained close to the walls of the dance hall.
According to the Oxford English Dictionary (2nd ed), the first known usage of the term in this sense was in an 1820 poem entitled County Ball by Winthrop Mackworth Praed. It was originally used to refer to women, and only in the context of dances; more recently the term has been expanded to include men and other social gatherings.