If you want to find out whether a name is already registered as a trademark for a particular country, you have to check the national brands of that country, as well as IR trademarks and EU trademarks, if the country is in the EU. For a full trademark search you have to take a thorough look through all relevant trademark registers. Searching for national trademarks alone is not usually enough!
If you want to check your name for Great Britain, for example, you need to check the database of the Intellectual Property Office (which contains trademarks registered in the United Kingdom), the EUIPO (includes EU trademarks which also apply to Great Britain) and the WIPO (includes IR trademarks which may also apply to Great Britain). In Switzerland, you apply to the Swiss Federal Institute of Intellectual Property (where Albert Einstein worked from 1902 to 1907) and the WIPO. EU trademarks have no protection in Switzerland, so the EUIPO directory is not relevant there.
Almost all trademark databases offer a free online search. Using it can be cumbersome, particularly if you want to research several ideas at once. You need to enter all names and their different variations on several search forms. You can save a lot of time by using NameRobot's Trademark Check which was specifically designed for this purpose. It checks all databases relevant to your country with a single click and looks for identical trademarks. This saves a lot of time, not only because you need to enter your name idea onto just one form, but also because you don’t have to tackle all sorts of different search forms on the internet.
For a more thorough trademark similarity search or a professional assessment of the risks of a trademark application, you should seek advice from a specialist lawyer. Please notice, that NameRobot's Trademark Check is steadily growing but doesn't yet contain all trademarks of all countries. At the moment you can research trademarks of the United States, the European Union and Switzerland.