It could be about family bonds.
The theme might be the closeness and special connection between siblings. Since it's about being 'in the sister's belly', it could symbolize a return to a very primal and protected state within the family, highlighting the deep - rooted relationship and the sense of security that comes from the sister - brother or sister - sister relationship.
I'm sorry, I haven't read this story so I can't summarize it directly.
Perhaps the theme is about discovery. If new words were added each day, it might be like the discovery of new ideas or elements in a story. The story could be about a character exploring a new world, and each day's word represents a new discovery within that world. For instance, if one day the word was 'mystery', then a mystery element could be introduced into the story's plot.
The theme might be about self - discovery. The story could be about a character's journey within themselves over the course of the 1385 - word narrative. They might face challenges, learn new things about themselves, and ultimately grow as a person. For example, they could start off feeling lost in life and through various experiences described in the story, find their true purpose.
Since I don't know the details of 'day 209 word story', it could be any theme. It might be a love theme if the word was something like 'heart' or 'affection'. Or it could be a adventure theme if the word was 'journey' or 'explore'.
Since we don't know much about the 'day 420 word story', the theme could be quite diverse. It could be a story centered around nature if the writer spent a lot of time outdoors during those 420 days and was inspired by the beauty of the natural world. It might also be a story about perseverance, especially if the writer faced difficulties during the writing process or in their life during that time. Or it could be a humorous story, perhaps the writer used the 420 days to come up with comical situations and characters.
Without reading the 'day 477 word story', it's just speculation. However, some common themes in stories are love, family, and survival. It could be a love story, where two characters fall in love against all odds. Maybe it's a story about family values, how a family overcomes challenges together. Or it could be about survival in a harsh environment, with characters having to fight for their lives and make difficult choices to stay alive.
Perhaps the theme is about change. The word 'metamorphosis' comes to mind. Just like a caterpillar changes into a butterfly through metamorphosis, in life we also go through various changes. Day 271's word story could explore how people adapt to change, whether it's a change in career, relationships, or personal beliefs.
Since we don't know much about it, it could be any theme. Maybe it's a love story, or a mystery.
I don't know the 'day 39 words story', so I can't determine its theme.
The theme could be 'Word Discovery'. It might be about characters finding new and exciting words.