Does what something is 'designed' for really make a difference? Is that the thing that makes something a currency or not? Or is it some other thing that makes s

Does what something is 'designed' for really make a difference? Is that the thing that makes something a currency or not? Or is it some other thing that makes something a currency? The value of some currencies have fluctuated in their value wildly in the past, so stability isn't a some intrinsic thing that marks a currency. I'm not say I don't agree that the word 'cryptocurrency" isn't banded about far too much, but saying "They aren't currencies" should be supported by some kind of description of what makes a currency a currency otherwise we can tie ourselves in knots. Saying that the 'design' or 'stability' define whether something is a currency as it is really just using proxies (that might work most of the time) for what makes something a currency. I think.