This is a rather obscure expression from someone's childhood invention of their own language. Not only does it rhyme, it also and sounds sort of like when someone mumbles and the sound can remind one of a shoulder shrug.

It's literal translation is "I don't know."

It can also me used as a distraction device when trying to get out of admitting wrongdoing because the two-word phrase itself sounds so bizarre as to throw off your interrogator.

It can be very effective used in a "broken record" or, more modernly, as a "scratched CD" fashion
Mom: Who took all the cookies from the cookie jar?
Tom: Sager Blager.
Mom: What is that supposed to mean, smartypants?
Tom: Sager Blager.
Mom: Can you speak Enlish, PLEASE?!!?
Tom: Sager Blager
(Mom proceeds to violently spank Tom.)
by Brent R.K. January 18, 2007
Get the sager blager mug.