Considering how some names were constructed, I would think (although this is from not being educated in how names evolved) that this could be fairly common...

• Relationships - Johnson (John's Son), Jackson, etc
• Occupations - Cooper (the barrel maker), Farmer, Hunter, Smith
• Variants on one of the above - Johnson, Johnston, Jonson, Jensen; Smith, Smithe, Smythe

I would surmise that you would see many common prefixes and suffixes being present among a large enough population of names.

This is, however, an interesting problem. I can see bringing this one out later on if any of my kids take an interest in programming.