Surnames, as I have noted previously, are fairly slippery. But the historical fact is that some surnames can be traced to a particular geographic area. Many surnames have multiple origins and occur in clusters in the country of origin. One reference on surname studies is:
Redmonds, George. Names and History: People, Places, and Things. London: Hambledon and London, 2004.
One place to begin your investigations is the FamilySearch Labs website Standard Finder. This section of the Labs website gives you a way to search for names, dates, places and resources. Using this resource, you can do a search on a word in one of the categories and get a list of the variations from historical records. Here are the variations for the surname Tanner:
mctanner, tanard, tanare, tanares, tanere, tanerin, taniere, tanire, tannar, tannard, tannare, tanner, tannerin, tanners, tanneur, tannier, tannir, tannor, tannr, tanyard, tanyer, tenard, tennard, teyner, thanner, thannerin
I can add a few more from phonetic transcribing on census records and other documents. Notwithstanding the variety of different names, these may all have a similar origin. An example of a useful website for finding surname distribution is the FamilySearch Research Wiki article on Surname Distribution Maps.
Surnames originated from given names (patronymics), places, occupations, personal attributes, plants and animals. Of course, there are numerous variant name spellings. Here is a website with a variety of different name spellings: American-French Genealogical Society, Surnames. You might look for lists of the spelling variations of your own name. You may also wish to check out the websites for the Guild of One-name Studies.
Spelling is a bugaboo. Many people insist on the way their name is spelled and also assume it has always been spelled that way. You learn that this is a myth after only a few hours of searching for your ancestors. This is especially true when you find out your ancestors did not know how to read or write and did not know the "correct" spelling of their own names.
This can be an very interesting study. There are aspects of name studies that can have a huge impact on researching families, but most of the time we are confronting problems with legibility, transcription and hearing.