Bonds that at the time of issue were considered investment grade but that have dropped below that rating over time.
The fallen angels are those angels who followed Lucifer in the Great Rebellion, whose consciousness therefore "fell" to lower levels of vibration. They were "cast out into the earth" by Archangel Michael (Revelations 12:7-12), constrained by the karma of their disobedience to God and his Christ to take on and evolve through dense physical bodies.
Refers to bonds that were investment grade at the time of issue but have since declined to below investment grade (BB or lower). The difference between fallen angels and junk bonds is that fallen angels were originally of investment grade whereas junk bonds never had an investment grade rating.