So if a currency goes up in value, that's actually economic 'deflation', because the prices of goods go down.

Now - I don't agree with any of the commenters arguments at all, but the terms 'inflationary' and 'deflationary' are used in that context.

There are some that argue the inflation and deflation are not a function of the price of goods - rather - simply the amount of money in circulation and that's it. I think this is the Austrian position.