Why is the rising price of a commodity inflationary, while the rising price of money is disinflationary?
If everybody borrows money, where can you borrow money from? 

In what unit do you denote the price of oil, chocolate, or cows? Well, in units of money. So calling interest rates the price of money doesn't quite make much sense. 

You can think about it as the price of money today in terms of future money though. So an increase in interest rates makes money today more expensive in terms of future money, which is the same thing as making future money cheaper in terms of money today. And if future money gets cheaper, more people might "buy" future money (usually, we call that saving). 

The more future money people buy with money today, the less money they have left for oil, chocolate, and cows. But we already have all the oil, chocolate, and cows around. So that people still buy these things, oil, chocolate, and cows have to get cheaper and the price level for goods and services measured in money today goes down. Less inflation.