why Angular JS is named Angular JS?

Because Angular JS can be written inside the angle brackets of HTML that is why it is known as Angular JS .

The use of 'ng' commonly in all its directives is to make the browser understand that this html page is making use of aNGular JS(Note the capital Letters)

Just googled: "why is angular js called angular".

Result: https://docs.angularjs.org/misc/faq

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

Because html has angular brackets and ng rhymes with angular, ng = next generation, as in angular is the next generation of html