The idea came from somewhere else, just like Angels having wings or halos: it's never actually mentioned in the bible, but someone painted it once, it became popular culture, so now it's a common belief.

The idea of a world currency is guesswork. Basically in the bible the antichrist (or whomever) will rule over every nation, person and language. So, it's assumed that in order for this to happen it has to be a one-world government and are therefore using a one-world currency.

This confirms, however, that it couldn't possibly be Bitcoin or any other alt currency. They are mostly decentralized. A one-world currency would need to be a government created and owned cryptocurrency or fiat. Or maybe there's no currency at all, it's not a requirement.

What I find most interesting about the end times though is that fictional writers (books, TV, movies) always show "good people" trying to stop the end times from happening. But, if it's something that's prophesied to happen and it's God's Word, wouldn't Christians actually want to hasten the arrival of the end times? Trying to fight the inevitable is foolishly working against God, and a complete waste of their purpose.

Anyways, I always thought it would be a cool idea for something in fiction: people trying to kickstart the apocalypse are actually the ones in the right.