Kristina, a lady who was standing near me when I burst into laughter (and who understood why I found it to be so funny when I explained why I was laughing) told me about the actual provenance that you linked to...
I realize now it's just an unfortunate coincidence, but not having been familiar with the Marionberry, and being a Washingtonian who well remembers the late crack smoking mayor, seeing it for the first time sitting on the ice cream shelf between the Chocolate Chip and the Rocky Road was hilarious...
A blackberry by any other name.
We have wild blackberries in the woods by the house in Pa. Blueberries too.
I usually pick em and pour some heavy cream on them. MMMMM MMMMMM good.