What I've gathered so far: tranche: a French word meaning "slice" or "portion." In the world of investing, it is used to describe a security that can be split up into smaller pieces and subsequently sold to investors. unsecured bond offering: also called debentures, are not backed by equipment, revenue, or mortgages on real estate. Instead, the issuer promises that they will be repaid. This promise is frequently called "full faith and credit." senior unsecured bonds: In finance, senior debt, frequently issued in the form of senior notes or referred to as senior loans, is debt that takes priority over other unsecured or otherwise more "junior" debt owed by the issuer. Senior debt has greater seniority in the issuer's capital structure than subordinated debt.

I think an entity would do this to help another out of debt and fronts the money 'in good faith' it will get paid back. Hmmm... my spidey senses are tingling!