A word with an odd etymology
Interest originally meant “to be between” or “to matter,” not to make money.
In Latin, inter esse described something that affected a situation or created a difference.
Early Roman law used “interest” to mean compensation for loss or delay, not profit.
Lenders claimed interest as the difference between what was owed and what was actually delivered.
Medieval Christianity banned usury, defined as charging money for the mere passage of time.
To keep lending alive, thinkers reframed extra payments as compensation for loss, risk, or missed opportunity.
These payments were justified by saying the lender had an “interest at stake.”
The word “interest” sounded relational and neutral, unlike the morally loaded word “usury.”
Over time, interest replaced usury in language even when the economic behavior stayed the same.
By early capitalism, interest was normalized as the return on money lent through time.
The moral debate faded, but the semantic shift remained embedded in law and finance.
Interest today still carries the older meaning of “what matters,” disguised as a technical price of money.
Language allowed profit from time to appear as fair compensation rather than exploitation.
This is why critiques of debt often target the concept of interest itself, not just the rate.