Ceit Butler
Wow, did that connect a lot of dots. I started reading up on the Bank for International Settlements. The "About" page is full of fun words to look up! "Prime Counterparty" led me to this:
http://en.wikipedia.org/wiki/Prime_brokerage
...which led me to this:
http://en.wikipedia.org/wiki/Hypothecation
...and specifically, this section:
http://en.wikipedia.org/wiki/Hypothecation#Rehypothecation
Which describes the exact method by which banks borrow overnight from The Bank of Canada.