‘Pranava’

The Sanskrit term ‘nava’ means ‘new’.
Pranava (the term used to refer the sound of ‘AUM’) can be split as ‘pra’ + ‘nava’ .
The prefix ‘pra’ can be taken as a prefix divinity to any object [for instance, sAda refers to purity, and pra-sada is any divine offering that is done to the Lord]
Every time the Pranava is chanted, it takes one to a new plane of divinity and brings a novel transformation.
That is perhaps a reason why it is termed ‘pra-nava’!