The Dictionary of American Family Names, from Oxford University Press, is one of those must-have resources for serious genealogists. Each entry gives a detailed origin of a family's surname, describing its various meanings, geographical origins, and the context in which it arose.
In fact, the venerable Genealogy Bulletin says "it belongs in every library in America , particularly those who cater to genealogists".
Too bad the danged thing cost hundreds of dollars for the three-volume hard copy set.
Happily though, you can get online access to DAFN absolutely free, using the Surname Lookups at Ancestry.com
Getting there is a mite tricky. From the Ancestry.com homepage, just click on the tab labeled Search (or click on Search All Records from the pull-down menu). Once on the Search page, scroll down. Near the bottom, on the right hand side, is Other Resources, and just under that is Surname Distribution. That's the one you want...click there, and search on your surname.
As far as I can tell, the lookup includes all 70,000+ surnames from DAFN. Even more, you can also look up the etymology of first names...still at no charge. A pretty good deal!
For those having trouble finding the right page at Ancestry, here's an alternative link you can try.