kääduvad

Could you specify what “kääduvad” refers to? I’m not finding a widely recognized definition in standard sources. To write a clean, neutral wiki-style article under 300 words, please provide:

- the language or field (for example Estonian linguistics, anthropology, biology, or a fictional universe),

- whether it is a real term or a fictional concept, and

- any context or source you want reflected.

If you’d like, I can also create a concise, fictional encyclopedia entry with a defined background.