I am not an attorney, but here is a quote from a book available
for purchase at
http://www.nolo.com , titled "Getting
Permission: How to License & Clear Copyrighted Materials Online
& Off", and authored by Attorney Richard Stim:
"In Chapter 8 we explain that titles and short phrases are not
protected under copyright law. However, despite their public
domain status, names, titles and short phrases may be
protected under trademark laws. Take, for example, the
slogan "Just Do It." It does not qualify for copyright protection.
You can use it in a song lyric, movie or in your book. However,
because it is a trademark, you cannot use it in a manner that is
likely to confuse consumers into thinking that you are associated
with Nike, or in a manner that tarnishes Nike's reputation. For
more information on customer confusion and tarnishment, see
Chapter 10."
Applications for copyrights are submitted to the U.S. Copyright
Office, a department of the Library of Congress. Their web site is
http://www.copyright.gov/
Applications for patents and trademarks are submitted to the
U.S. Patent and Trademark Office, an agency of the U.S.
Department of Commerce. Their web site is
http://www.uspto.gov/