surname Blum #names

Barbara Douglas

I’m trying to trace my grandfathers ancestors.  i believe the name had been changed. 
why is BLUM such a common name?   growing up
in michigan there weren’t that many, but in NYC There are a million.  i’ve not be able to find his naturalization papers, but his records show he was was Satanov/Sataniv.  His grave is also in a section with that city designation.  Any recommendation as to how i might find his original surname?  
thanks for any suggestions.  
Barbara Blum

snyder lipsky bemdersky grossberg

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