Earlier quoted context omitted.
I'm reading Graeber's Debt, the first 5000 years which explains how this practice is as old as debt itself. It already existed in ancient Mesopotamia. I highly recommend this book to anyone interested in the topic. It also shows how debt is deeply linked to slavery, women slavery in particular, through the phenomenon of debt peonage.
Sounds awesome - will have to check it out. Totally random aside: does it talk about the evolution of debtor's prisons after slavery was no longer an option? I always wondered why people thought it made sense to lock someone up with no economic recourse to pay down a debt. There were probably much better options to deal with the potential moral hazard.
http://en.wikipedia.org/wiki/Debtors'_prison
Labor was one form. I imagine being sent to prison moved families to action to bail out the debtor when possible.
Finally, consider all the debts paid to avoid going to debtors prison.
I don't know anything about the evolution of the system. Just pointing out that it wasn't an insane way to acheive the goal of debt payment. (Though a totally inhumane way)