Investopedia defines an “angel bond” as a bond that has a lower interest rate because of the issuing company’s high credit rating. “Angel bonds” are said to be the opposite of “fallen angels”—formerly solid companies (“angels”) that have dropped (“fallen”) precipitously in price.
 
Citations for “angel bond” have been very rare and mainly quote the Investopedia definition (from 2010). It is not possible to say when “angel bond” was coined, or even that it is a legitimate term, because of the lack of legitimate citations.
 
 
Investopedia
What Does Angel Bond Mean?
Investment-grade bonds that pay a lower interest rate because of the issuing company’s high credit rating. Angel bonds are the opposite of fallen angels, which are bonds that have been given a “junk” rating, and are therefore much more risky.