The word is clearly from the Latin for 'world'. If you are a Buddhist, a pro commerce person or you are in the tradition of 'aliveness'; then being part of 'this world'...'be here now' is to consider Mundo to be of the highest value in daily life.
So how did 'mundane' get the terrible connotations that it has in our current language?
For two reasons. One is mainstream religion: Christianity, Islam and the other religions that promise a heavenly afterlife. If there is a heavenly after life then anything in the current life is subsidiary, inadequate 'mundane'.
The second is Leftism, Environmentalism, eschatology, Heideggerism, communism, socialism, Rousseau, Marx and every offspring of the French Revolution. This is all one anti-commerce package that imagines an ideal world that is better. Making our current live mundane in the most negative meaning of that word.
The meaning of mundane must be made current. I love mundane. I love commerce. I love being alive in this world. Praise be to mundo, bless us all.