In the 1920s, the phrase "egg" was often used as slang for a young person, particularly in the context of the burgeoning youth culture of the time. It could indicate someone who was inexperienced or naive. Additionally, "egg" could refer to someone who was trying to be stylish or trendy but might not fully understand the social nuances of being part of that scene.
The 1920s were a time of significant cultural change, and slang was a key part of the social fabric. Terms often evolved quickly, so meanings could vary by region and social group. If you were looking for a more specific context or usage, feel free to provide more details!