1. Data: The frequency of the substring 'flapper*' displays significant variation over the decades. Notably, it remains absent in the 1820s, 1830s, 1850s, 1870s, and 1880s, indicating a lack of usage during these periods. The term begins to gain traction in the 1860s and sees a marked increase in the 1920s, where it peaks dramatically. Following this high, the frequency experiences a gradual decline through the mid-20th century and into the 21st century, with a notable resurgence in the 2000s before stabilizing in the 2010s.

2. Possible explanation: The dramatic rise in frequency during the 1920s can be attributed to the emergence of the "flapper" as a cultural icon representing a new generation of women characterized by their progressive attitudes, fashion, and behavior in post-World War I America. This cultural shift likely led to an increase in literature and discourse surrounding flappers, capturing the essence of the Roaring Twenties. The subsequent decline in the later decades may reflect changing social norms and the fading prominence of the flapper image, as newer cultural phenomena emerged. The fluctuations seen in the 2000s could indicate a revival or nostalgic reference to flapper culture, perhaps in literature or media, as cultural cycles often revisit past trends.

3. Competing constructions: In decades where 'flapper' is relatively infrequent, other terms may have been employed to describe similar cultural or social phenomena. For instance, during the 19th century, terms like "lady," "socialite," or "feminine" might have served to describe women’s roles without the specific connotations of modern independence and rebellion that "flapper" encapsulates. In the later decades, particularly the 1950s and 1960s, alternatives like "housewife" or "bohemian" could have been used to reflect different societal expectations, thereby fulfilling similar communicative roles without the specific cultural implications associated with 'flapper'.