It's interesting that RDR2 references Cornwall so much
The game seems to love referencing various locations or parts of Cornish culture. We've got:
Leveticus Cornwall --> His surname is Cornwall.
Josiah Trelawny --> Trelawny is a Cornish surname, and Trelawney is used as many Cornish business names.
Arthur Morgan --> A bit more on the nose. Referencing King Arthur and Morgan le Fay, both characters in Arthurian legend which has very strong ties to Cornwall.
Epilogue --> Using the alias of Lancelot, again a direct reference to Arthurian legend
Saint Denis --> St Dennis is a town in Cornwall
New Austin --> A bit of a stretch, but St Austell is a town in Cornwall
Blackwater --> Blackwater is a town near Truro, Cornwall
I know that RDR2 was made primarily in Rockstar North in Edinburgh, but that's a long way from Cornwall, so it's interesting that the game has so many references. There's probably more, but that's what I've found so far :)