Answer:
The "-ism" that was trending during the 1920s was **Modernism**¹².
This was a period of great social and cultural change, often referred to as the "Roaring Twenties" or the "Jazz Age". It was characterized by a break with traditional styles and the embrace of new, modern ones¹². This was evident in various aspects of society, including art, architecture, music, and fashion¹². The Art Deco movement, which was part of Modernism, had a significant influence on design and aesthetics during this period². The era was also marked by a shift in societal norms and values, with a greater emphasis on individualism and a rejection of older, more conservative ideologies¹²..