Why is a group of apes calleda shrewdness?

A group of apes is not called a shrewdness. That's a term used for a group of weasels.

There isn't a universally accepted collective noun for a group of apes. Some common terms used are:

* Troop: This is probably the most commonly used term.

* Band: Another frequently used term.

* Congress: This term is used to describe a gathering of chimpanzees.

* Herd: This term is sometimes used for gorillas.

There are other, less common terms, but those are the most prevalent.