I hope I am posting this in the right board.
Trademarks are used to avoid confusion between competing offerings. If the offerings are clearly not competitive and unrelated, then I believe (I am not a trademark lawyer) there is no restriction on getting a trademark.
So, for instance:
So you could potentially use "emew" for your application name, so long as there is no potential confusion with the other usage. Getting something where the .com is available is another question! There is only one crystal.com, even though there are many trademarks who might want it!!
EMEW is registered for Electrowinning machines, namely machines which allow metals to be extracted from metallic salts.
If you're developing software I think you should be good. Perfect Example search "King" 10K+ results, and that's just registered.
Trademarks as Kamal said are to protect confusion, not necessarily to make it impossible to name companies or drag businesses to court
The trademark "rule" you're most worried about deals with confusing similarity -- your mark cannot be so similar to another mark that consumers will be confused and think that your goods came from the other mark's owner, or vice versa. So, for example, you cannot have a hamburger place called "MacDonald's" when there's a "McDonald's" already out there -- people will think that you're part of that chain.
The further away you get that, the better off you are. So, for example, if your mark has the same letters as somebody else's, but is used on completely different goods or services, there's very little likelihood that anybody would be confused. (Delta airlines/Delta faucets, for example).
Note that marks don't have to be identical to be "confusingly similar" -- they're looking at the overall commercial impression. There are a lot of factors which go into making that determination -- not just the physical appearance, but how they sound, channels of commerce, how sophisticated the buyers are, etc...