Checking through things on my hosting where I have multi domain linux hosting with cpanel... I noted that there were multiple entry points to addon domain directories and sub domains. Every add on domain in a multi domain shared hosting plan is treated as a subdomain. Whenever we create an add on domain it creates a folder in the web root directory and hence can be accessed through the primary domain-slash-addon domain as well.. hence the duplicate content!
So how to get rid of the duplicate content hence generated?
I found this - https://perishablepress.com/prevent-duplicate-content-cpanel/ but the post is a bit confusing.
Seek a definitive guide/advice/tut on this.