The bulk update request #12965 is pending approval.
create alias noble (94) -> nobility (9)
create alias aristocrat (31) -> nobility (9)
mass update duchess_(title) -> noblewoman
create implication noblewoman (59) -> nobility (9)
create implication nobleman (27) -> nobility (9)
Reason: This would create tag infrastructure for this social class analogous to that which currently exists for royalty. The alias target is based on the existing royal -> royalty alias and the fact that nobility has a wiki description while noble does not.
duchess_(title) has only ever been added by one user, so I think it's safe to simply mass update it rather than alias.