Your chord is the fulcrum of a very extended musical pun
"it's something like an O Henry story, where the revelation in the last line makes you totally reconsider everything that happened in the story - every relationship, and everything you thought you knew on first reading, you have to put in a new light now ..." flug gives an amazing, detailed answer to cubeb's question, "How did Bach make this one jazzy chord fit into a Baroque chord progression?"
