The compound-conjunction 'and but so' and its occasional extensions ("But and so and but so...") were literary devices (or some would say, tics) used by David Foster Wallace in many of his works, but most particularly in Infinite Jest. It fit nicely into his jumbled ramblings, and indicates a moment of confusion in the way two events fit together.
"When somebody's talking and they get on a roll, and they start talking faster and faster -- and they don't breathe -- one of the things they'll do is have compound-conjunctions because you're really -- you're wanting that sentence to serve a number of things. It's both a contrast and a continuation, and it's an extrapolation. And it's a little unconscious clue to the reader that he's more listening than reading now -- that we're at a pace now that's supposed to be far more sound and pace and breath than it is these short contained sentences. ... Infinite Jest is the first thing that I wrote where the narrator -- it's supposed to sound like the narrator's talking to you."
-- David Foster Wallace
Because this phrase is very recognizable, it is often inserted into other works as a quick reference to Infinite Jest. It recently appeared in the popular young adult book Will Grayson, Will Grayson by John Green and David Levithan in the forms 'andbutso' and 'sobutand', giving it a bit of new life among angsty teenagers. Even so, it is fairly uncommon in every context except for blogs about David Foster Wallace... of which there are a a surprising number.