A collective of Collective Nouns
a congress, flange, rumpus, troupe
Just where do these crazy ideas come from?
Collective Nouns are a fun and inventive habit we have developed for referring to groups of things, people and animals.
You can learn more about how collective nouns work in grammar here
There is more information about the development of collective nouns here
Why not look at what study and learning resources we have available here