I've just been educated by Channel 5
The old name for pudding was either "Puddog" or "Puddick". Hence where the dick came from. It therefore follows that a spotted dick as we (probably) all know is a dick (pudding) with spots (the fruit). Slap on a drop of custard and you have an old fashion pud.
It, therefore, surprised me when they said that in 2018 the House of Commons changed the name. Gone was the Spotted Dick instead it is called a Spotted Richard!
What! The only reason I can think of changing the name is that the place is full of dicks and they didn't want there to be any confusion.
Ho Hum! Pass me the strawberry Pavlova and I'll show you an Eton Mess!