The first part of this is vavfather.
The second part of this word (nI') appears in other family related terms (like be'nI'sister and SoSnI'grandmother), but it is not clear what its literal meaning is.
Cite this entry
Definition of {vavnI'}
from the Klingon Language Wiki:
https://klingon.wiki/Word/VavnI-
Retrieved 03 Jul 2022