If you have read the sharing reason of my article
Note: It is just about showing others that wordpress theme used is a custom theme made by you not some one else. But if you are going to do this with a theme which you have to buy then please first buy it and do whatever you want on the specific site you bought it for otherwise do not use this article. I never support pirated stuff.
So lets get started in changing the stuff that is being detected to know which wordpress theme is used.
First change the wordpress theme folder name to the name you want.
Secondly change the screenshot.png in the folder.
Third the most important step is to change the style.css file. You will find it in the theme folder and you have to change the information in the first comment. It will look as following edit it with the information you want visible for public.
By making this changes in the theme folder and files of wordpress. Specially in source code of the sites Style.css. Then when you will try to detect theme names then Wordpress theme detecting sites will show your custom information. I hope you like it and is helpful to you. If you have any questions please feel free to ask us.