1 Terry: What sort of security and safeguards will there be for the nuclear material in here?
2 Simon: Oh, I hadn't thought about that. It might be locked in an old cupboard or something, I suppose.
3 Terry: Not a lead-lined safe or a special secure clean room?
4 Simon: Do you know how hard some of those old wooden cupboards can be to open?

Apparently there is some inter-dialectical confusion over the English terms cupboard, closet, and cabinet.

I tend to think of these terms as all more or less interchangeable, but usually default to "cupboard" to describe all of them (as I believe most Australians do, in my experience). I'd even go so far as to say that in my usage a closet is a specific type of cupboard (usually for clothes), and a cabinet is a specific type of cupboard (often built into a kitchen, but possibly also free standing, like an office cabinet).

It looks like there may be a bit more of a distinction in US English at least, maybe also British. Old Mother Hubbard, you have a lot to answer for!