Several times each day this question (or a variation) arrives in my mailbox. Sometimes it is from a woman who is getting married and wants to learn more about the name she will soon be adopting. Others come from people looking for the answer to a school assignment (when will teachers learn that asking students to learn the origin of their last name rarely teaches them anything useful?). The majority, however, come from people who are just beginning to look at their family tree and hope that learning the origin of their last name will give them insight into where their family originally came from.
Last names aren't always as simple as they sound, however. Kerry, for example, is an Irish surname. Yet, Senator John Kerry, the Democratic candidate for U.S. President, has Austrian origins - his grandfather changed his name from Kohn to Kerry after arriving in the U.S. As you trace the origin of your own last name, don't be surprised to find that its present incarnation has been changed from the original as well. You may have a slight spelling variation of the original name, an anglicized version, or even a completely different surname.
Difficulties aside, there is something neat about learning what your name means and how it was originally derived. Check the Glossary of Last Name Meanings & Origins for the meaning and origin of your family name.