Kenneth Fisher explains a couple of database name functions in SQL Server:
I’d never seen ORIGINAL_DB_NAME until recently and I thought it would be interesting to highlight it out, and in particular the difference between it and DB_NAME. I use DB_NAME and DB_ID fairly frequently in support queries (for example what database context is a query running from or what database are given DB files from). So starting with DB_NAME.
Click through to know when to use each.