The Fish and Parcels Line

I've read in quite a few places that one of the erstwhile nicknames for the DR was the Fish and Parcels Line. I always assumed that this nickname came about when the DR began running services to Windsor via Ealing Broadway, as apparently these services were associated with seafood and freight in some way.

Is this true, or was it made up by the same person who named the T&BWTKB as such?