Either the database has been "corrupted" with regards to some mandatory nodes not existing anymore (technically speaking an admin user could delete the critically important app:dictionary folder) or a configuration change in alfresco-global.properties has cause the folder to be bootstrapped with a different name than is currently being attempted for lookup purposes (it is technically possible to rename the "app:dictionary" name to any other value).
Do you have a database backup to try restoring from a working state?
A backup from a different environment database will not help you - you need the backup from that database. The specific procedure for restoring the backup depends on the way the backup was created and the type of the database - refer to the documentation for your database.
If you are very, very confident in your SQL / database skills you could attempt to recover sites (and contents) from the database without the application starting, but that would be quite some involved work even for me (at least to get it 100% right).