I love to bring this question up to my Irish friends every year, the ones who bleed green. And all I get is strange stares.
I grew up in a neighborhood in Philadelphia, Pennsylvania (USA) that was mostly Irish and Italian. As an Italian, I would love to pose this question to my Irish friends.
After hundred upon hundreds of inquiries, not one Irishman has provided an answer, or even an educated guess. Nothing… silence and stares…and this is before they start drinking.
My guess is that the potato-starved Irish Americans - fresh out of Potatos due to leaving Ireland as a result of the great potato famine - conjured up a “potato” from whatever they could. Throw some cinnamon on the outside to mimic the old dirty rough skin, and…voila! Potato!
Any help? Searches give tons o’ recipes and famine info.