Interest is MONEY earned by MONEY. Money as you know is that means of exchange that is printed by the Chief financial institution of a country. But interest has taken the power to print money in the economy illegally. Thus Interest is the legal way of generating illegal money. Since money is a means of exchange and ideally cannot earn money. So the money earned by interest becomes fictitious money, money that does not exist. Thus amount of money generated by way of interest inflates the quantity of money in the economy.
Now this money taken on interest is lend further on higher interest by middlemen, i.e.banks and other lending institutions. The money generated by higher interest further inflates the quanitity of money.