Fair enough - not doubt I am one of the offenders.
BDC - business development company. This is a business model that operates as a RIC (registered investment company). RIC's are subject to certain legal restrictions that dictate the nature of RIC's. Important among these is the limit on leverage 1:1 and the requirement to pay out at least 90% of earnings annually. Other laws impose an excise tax on the 10% that is not distributed UNLESS at least 98% of income is distributed. Because of this law BDC's often distribute at least 98% of income each year.
SIV - structured investment vehicle. I know much less about these but view them as a "trust" of sorts that pass through ownership of various investments to unit holders.