Jim, According to information I got from a web page created by Maggie Stewart-Zimmerman, (homepages.rootsweb.com/~maggieoh/mpreble.html), Preble County was named for Captain Edward Preble, a distinguished naval hero of the american Revolution and the Tripolitan War. You can find out more about him at www.usspreble.org/commodor.html.
As to the number of "Prebles" in the county, you might want to check out the following web page: www.hamrick.com/names. You can check out how frequentlya surname appears over different periods in history. As of 1990, there were more Prebles in Maine, New Hampshire, North Dakota and Wisconsin than there were in the whole state of Ohio!