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?