This is a currently fashionable marketing term for pre-teens, girls in particular, aged between 7 and 11, a group having substantial purchasing power. They are more worldly-wise, fashion-conscious and media-aware than children of this age used to be, and are growing up faster. It’s a younger group than that identified by tweenie. The term has appeared sporadically since the 1980s, though early sightings suggest it used to refer to the 10 to 13 age group, and the Oxford English Dictionary database has an example from 1952, in the title of a book by A A Macfarlan: New Games for Tween-agers. But it has become more visible only in the past couple of years or so, even though it is still principally a specialist term within the marketing field. In Britain, people have become more aware of it as a result of a recent BBC television documentary, “Little Women — A Day in the Life of a Tweenager”. The word is obviously formed from the second part of between, on the model of teenager.
If you think teenagers are growing up too quickly, take a look at their younger sisters, the 7 to 11-year-olds the marketing industry has branded as “tweenagers”.
The Guardian, Mar. 2001
Kids Klub and Tweenager Club for pre-teens meets Wednesdays.
Tampa Tribune, Mar. 2000