I also think it's interesting to understand the origin of interest. Before private property rights, say we live in a clan or a tribe or a feudal manor and we both produce grain. That is all we do. At the end of the year we combine our harvest and divide it accordingly. If I have a bad year that's ok because you might have a good year. All is well.
Introduce private property rights and now I own my farm and whatever I produce and you own yours as well. There now exists existential uncertainty that I could have a bad year and be worse off as a result - which didn't really exist before when everything was shared. So how do we mitigate this new risk? We produce and store a surplus of grain, so that given a bad year we can tap the surplus and be ok.
What happens if you have a particularly bad year and you deplete your surplus? You can come to me and ask to borrow some of my surplus. I will agree to this, but only with interest. Say I lend you 100 bushels, I require that back plus 10 more over the next few harvests. Why? Well it is not because I think you will default on your obligation. In these primitive times I could make you my bonded laborer or even have you killed. So what is it then that causes me to ask for interest on my loan to you? It is because if now I have a bad year, my surplus is smaller than it would have been if I hadn't given some to you. My existential risk has increased and that demands additional return to compensate.
Financial credit risk came along only later and this is simply a premium added above the base interest.