How correctly to use the names or part of the name of an existing project?

When creating a project, there is a question about its name. It's like giving a name to your child. I want it to be as unique as possible, rare and at the same time memorable.

But there is a temptation to use the name of already existing projects, slightly changing it, but leave the general sense the same.

For example:
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youtube.com VS rutube.ru
myspace.com VS My Place
classmates.com VS classmates. py
linkedin.com VS VKontakte

And this list can be continued further. But I would like to hear your opinion, to what extent is this correct and justified?