An interesting 80’s phrase with a deep past. The word “duh” had been used to express bewilderment or ignorance since the 70’s, but adding “no” to the front created a sarcastic expression that points out the obvious. Replying ‘no duh’ to a statement made my another showed that you were way ahead of them when it came to putting things together.
“Sheena Easton is wicked hot.”
“No duh, man.”