Is there such a thing as a single malt vodka? NB: There are products branded as single malt vodka (so the quick answer is Yes), but my question is more about whether such statements have any real meaning?

More detail

In a discussion the other day a friend pointed out that whisky (/ whiskey) isn't whisky until it's been aged in a barrel for some time.  Before it goes into the barrel it's essentially vodka.

That triggered a thought; the "malt" in malt whisky refers to it's being made from malted barley.  As such, I assumed that were you to take the pre-aged whisky ("new make spirit" / vodka), that must therefore be a single malt because it has the same malt as the whisky which would be made from it.

My friend pointed out that the single malt whisky is a single malt not because of the malt going in, but based on what comes out of the barrel; i.e. if made in a single barrel it's a single malt, if the combined contents of multiple barrels it's blended.  Thus, he argued, calling something single malt before it's been aged makes no sense, even though the ("single") malt is put in before the aging takes place / "no malts are extracted by aging".

I guess the argument's similar to talking about cake mix; i.e. if I baked a chocolate sponge and a vanilla sponge I'd get 2 cakes which would be distinct (even if I mashed them together a bit), whilst if I blended the cake mix I'd only get one cake / technically it was baked from a single mix even though that mix was itself a mix of mixes / the term single cake mix has no real meaning here (so single malt vodka wouldn't either).
I think you (and your friend) are confusing two similar terms.

&quot;Single Malt&quot; - the making of spirit from a single type of grain by a produced by a single distiller (for whisky, that's malted barley in the UK and malted rye in the US)
&quot;Single Barrel/Cask&quot; - the process of bottling each aged cask of liquor separately without mixing the casks together first.

&quot;Blended&quot; refers not to blending of the various casks from one batch together, but instead to blending together whiskys distilled by multiple distilleries or blending single malt with grain whisky. From the Wikipedia article on single malt:

To be called a single malt whisky in Scotland, a bottle may only contain whisky distilled from malted barley and produced at a single distillery. The regulations of other countries may allow malted rye.
If the bottle is the product of malt whiskies produced at more than one distillery, the whisky is called a blended malt or vatted malt, or pure malt. If a single malt is mixed with grain whisky, the result is a blended whisky. Single malts can be bottled by the distillery that produced them or by an independent bottler.

So, in the case of &quot;single malt vodka&quot;, that apparently means

“So what is meant by single malt vodka?” Elena queried.
“Most often, single malt vodka is 100% malted barley as the only ingredient.”

If you look at brands of vodka that call themselves this, this seems correct. Valt,  Franciacorta Single Malt Vodka, East Coast Single Malt Vodka, and several others list the sole ingredient as &quot;malted barley&quot;. Whether it's aged or not seems to depend on the maker.