I usually answer the question by discussing the barter system first. then I ask them where their currency comes from. After a long pause, I continue.

A long time ago, Charlie Shrem had his "A Geek in Prison" series. One of the items that he talked about which stuck with me was that the prisoners used cans of mackerel as their currency in the prison. Since one person was willing to trade other things for Mackerel, it truly was a currency.

If you Google Charlie Shrem and Mackerel, you will find it... https://steemit.com/story/@charlieshrem/mackerelcoin-and-my-socioeconomic-observations-from-prison-part-1-by-charlie-shrem

At this point, the person I am talking to is usually finding the conversation too much to handle ... so I change the topic. Wait a couple of days ... Then, I get them onto Steemit - using the article above as a starting point.

:-)