Angularjs:

All builtin directives in angularjs are prefixed with ng-

ng---> means Angular 

The prefix ng stands for "Angular;" all of the built-in directives that ship with Angular use that prefix. Similarly, it is recommended that you do not use the ng prefix on your own directives in order to avoid possible name collisions in future versions of Angular.

Why is this project called "AngularJS"? Why is the namespace called "ng"?

Because HTML has Angular brackets and "ng" sounds like "Angular".

But it's not sound like angular brackets, anyway we can go as per the book..