[Ger-Poland-Volhynia] German or Lithuanian?

[Krampetz at aol.com]

Background:
My grandfather,  Osip Niewiera,   died in 1918.    All I know is what I've 
found 
online:
at Ellis Island,  he described himself "Lithuanian",   from "Lida Russia"  
(Lida Poland, today's Belarus) when he  emigrated in 1912.  His death 
certificate which 
has him as Joseph Niewiera from Russia.  Also,  my  mother's birth record 
in Lida 
naming him. My mother was quite young when he died, but her mother and she, 
identified themselves as Polish, from Poland.   
I have no idea where Osip/Joseph was from, or any clues of  his family.
 
Now I do understand that in his part of Poland, under Russian  control,  
all were told they were Russians and lived in Russia - though all  still 
identified their ethnicity by language and  religion.    I find also that Osip is 
Russian for Joseph.  
 
I just found a large number of Niewiera surnamed people on Familysearch.org 
 and nearly all, in the 18th & 19th centuries,  were in East Prussia and  
most had German first names.   I've also been told & confirmed,  that there 
is no "W" in the Lithuanian language.
 
My question then:
  Is his surname, Niewiera,   Lithuanian?   Russian?  Polish?  Or German??
  
Thanks,
Bob K.