Why do we call a 100 year bond a bond?

Long title incoming<br><br>Why do we call a 100 year bond a bond and a 30 year house loan a mortgage? And why do we call a 30 year loan to a business that is backed by real estate a mortgage and a 30 year loan to a business that is backed by other collateral a bond?<br><br>Edit: a better question is <br>Why do we call 30 year loan a mortgage and a 10 year loan a house bond?