In recent decades thousands of people  have been involved in the "crowdsourcing"  of transcribing old documents containing information of a genealogical nature (census, court, probate, military and other records).  The greatest example of this are the records indexed by FamilySearch - literally millions, if not billions of names transcribed by human indexers.  Also in recent decades, machine/computer  based transcribing / OCR technology has really come of age.  The Google Book search feature is an example of this.   All in all - this indexing of documents and books is an incredible boon to genealogical researchers.   However one has to consider that both human and computer indexers will never be 100% accurate - just because of the nature of the items being indexed.   Yancey genealogists especially, need to be aware of how "mis-transcriptions" may influence and affect the results and interpretation of their genealogical research using tools that rely on indexing/transcription.

Because of various reasons, but often because the original documents are so hard to read - names can often be mis-indexed or mis-transcribed in databases like those at familysearch or ancestry.com.  

Here in the link below is an example of a Yancey family whose name has been been indexed as ZANCEY on familysearch indexes.

Here below are the most common mis-transcriptions for the name YANCEY/YANCY   ( documents have been mistakenly transcribed with these name spelligs when it shoudl have been Yancey/Yancey).  In searching genealogical indexes/databases - it is often a good idea to look for variant spellings such as these because of the possibility of variations in name indexing.  Only those with an “ * “ appear to be legitimate spellings of other names that have sometimes been mistranscriebd as Yancey.  (for example Zancey does not appear to be a legitimate name – but YOUNG surely is – both are spellings that in some cases have been mis-transcribed for persons by name "Yancey".

see also this link

YONCEY
YANEY
YAMCEY
YANSEY
YANSY
YANCEE
YONCEY
YONCY
YANCI
YANCYE
YANTZEY
YANTZY
YENCEY
YENCY
ZANCEY
ZANCY
YAUNCEY
JANCEY*
JANCY*
YOUNG*

As an interesting exercise – look for these names on a database like findagrave – where so often we have a photo of the engraved name on the headstone – and you will note most of these names just don’t exist.

Researchers also have to seriously consider the opposite - the fact that in some cases names which are totally unrelated to Yancey/Yancy  have been mis-transcribed as Yancey/Yancey/Yansey - most especially in massive databases of indexes to records originally written in cursive hard to read writing.  In a database with billions/millions of names it is almost certain there will be more than just one or two - that have been mis-transcribed as Yancey.

Here is an example of an English Census record that sure appears to be the name JANCEY - that has been indexed as Yancey.

The most common legitimate names to be mis-transcribed as Yancey/Yancy/Yansey include the following:

TANSEY - Irish name
JANCEY - English name
JAUNCEY - English name
YAXLEY - English name

How does one know for sure if a name that has been indexed as Yancey/Yancy - really was such?  In some cases it can be difficult to tell?

Here are some tips as to how to judge.

• See if you can look at the original document (a scan/microfilm of the original) .  As an example - there are various (less than 100 or so) entries for the name Yancey/Yancy on European records in familysearch databases.  When one looks at the originals in many of these cases these seem to be very hard to read entries where there is clearly the possibility/probability it is some other name totally unrelated to Yancey. 
• Check similar records of the time period - where mis-transcription would be much less likely. For example:  names engraved on grave stones (such as at findagrave.com).  Or printed material  where there is no real question as to the spelling - such as government published material, books of the period,  city / phone directories etc.
  Note as an example - Findagrave appears to contain not a single entry for a Yancey/Yancy grave in Europe (except for American soldiers abroad).
  If you find a family supposedly by name Yancey on a census record – look for the same family on census records before and after to see if they also show up in prior and successive years with the same spelling.
  
• Cross check one source against another.  For example one may note a Yancey entry in the area of Herfordshire, England.   But when one checks other sources like census and other records -  one notes that the name JANCEY/JAUNCEY is a common name in the region.  There are known cases of this name being mis-transcribed as Yancey.  Or for example if a US immigration record is found with a supposed Yancey coming from England - cross check it against subsequent US census records to see what name spelling is used.
• Even in some cases where the originally spelling seems to be perfectly clear as "Yancey"  one has to consider rare cases where the person (such as a census taker) wrote down what he thought was the name - when in actuality it wasnt recorded correctly.   When one considers the massive nature of databases like those at familysearch- one has to consider that there will be even a handful of such cases where even on the original document the name seems to be certainly spelled as Yancey - when in actuality the name has  been written in error.  Using cross referencing of other related sources - such as discussed in bulleted items above - will help clarify this situation. 
• Realize that what seems to have been is not always what actually was.  As an example - - if one looks in phone books etc. of European cities - - one can indeed find in a few very rare cases - the name of Yancey/Yancy.   Many of these have been found to be black Yanceys  whose family came from the country of Liberia - and whose ancestry originally traces back to slaves who left America and brought the name to Africa and later Europe. Also one has to consider the possibility of Americans traveling abroad - and even being born and married abroad. 
•  If a certain spelling existed in a certain region over a period of time - - one would think it quite possible that persons by such name/spelling still may exist there today.  Using such social media as Facebook, Twitter, Linkedin and many others - one can often locate people of a certain name in a certain region.  Or conversely one can show that the name is totally absent from a given region.  As an example even after heavy analysis of LINKEDIN - I have yet to find a single Yancey/Yancy entry  in Europe that didnt have connections/roots in America.
  Note that systems like FACEBOOK  have BILLIONS of users - users that can often be searched within a few clicks of the mouse. 
• Try checking Google book search for books printed in the region/time period.   Realize that even Google's OCR technology often gets the name wrong on older documents.
  One interesting exercise is to see if one can find the name of Yancey on any European document earlier than 1800 or so.
  see this as an example of a mis-index.