Hmmm... That came as a surprise to me, so I decided to look it up - and of course share my findings!
My initial search for 'cupboard' revealed that there is a kitchen store in Fort Collins known as The Cupboard. I found this amusing because ... well, the person I was talking to will know why it was amusing, and I'll just leave the rest of you guessing!!!
Continuing my search, I found that a cupboard is a closet with doors on the front, and shelves inside.
But wait -- I found something else that said a cupboard is a piece of furniture and a cabinet is more like a closet.
So -- is a cupboard a closet, or is a cabinet a closet?
Cabinets are typically considered general-purpose storage, while cupboards are more for food and dishes.
All right, that makes sense to me. Except that now I see that:
A cupboard is the more general-purpose receptacle, whereas a cabinet is more specific (e.g. medicine cabinet)
So -- is a cabinet general purpose, or is a cupboard general purpose???
Well. This is getting worse and worse. I decided that perhaps I needed to attack this from a different angle, so I decided to explore this from the regional/US/British standpoint. And I found an article online that discussed British and American English... and focused on the words 'cupboards' and 'closets'. Just what I was looking for... surely there will be answers here.
Sadly, this wasn't very helpful, as the article mostly talked about closets - which in England were initially private rooms, and then morphed into small rooms... and so you have water closets (ie bathrooms).. and besides, the British most commonly used wardrobes to hang their clothes, and so closets are rarely discussed.. and then of course you have broom cupboards and broom closets, which are the same thing.. which gets me absolutely nowhere.
So I checked out Wikipedia... and according to whoever wrote the page I was looking at (you do know that those are mostly ordinary people, right? They're not experts or anything) said that originally cupboards were open shelved storage cabinets, but now the word refers to a closed piece of furniture.
Ok... so a cupboard is a type of cabinet.... what does Wiki say a cabinet is?
According to Wiki, a cabinet is a body of high-ranking officials.
Actually, this makes more sense than anything else I've read today. Let's call the governmental bodies Cabinets. At a quick count, there are over 100 countries that have a Cabinet as part of their government.
All right.. We've got that settled... now, what about Closets? Oops... Wiki says closets are cabinets or cupboards.
And I'm back where I started.
A Cabinet is a governmental body.
And of course the Cupboard is where I keep my tea!