In many countries including the U.S., the U.K., and Canada, users build rights to a name merely through use, without ever registering that name as a trademark with any government. These are called Common Law rights.
So even if a trademark application hasn't been filed for your name by someone else, you can still run into trouble if your name is too similar to a name someone else is using for similar goods or services. It is this combination -- similarity of name plus similarity of goods -- that causes the trouble. (In fact, this similarity is also the most frequent reason a trademark application is rejected.)
An identical or similar name for unrelated goods should typically not be a problem. A useful way to think about this is, is there a likelihood of consumer confusion between their name use and yours?
It is due to these Common Law rights that -- once you have eliminated all your risky names based on the registered and pending trademarks you see here at Naming Matters -- it's important to conduct some further searching of your best name candidates using tools like Google.