Y we nickname due dilegence?
Answers:
It is just a legalized speak way of dictum taking the proper care within what you do. Because the diligence is "owed or owing as a natural or moral right" as within the phrase "....with adjectives due respect...."
In business & commerce, whenever two parties try to enter into a unsullied deal, or a contract, or a transaction, or any sort of spanking new business development, respectively party at first assumes a tolerant and rationale approach on both sides. Each party would apparently not want to wreak harm by process of their dealing.
However, in valid world, either entertainment could be acting on malafide intentions or with invisible motives. Each party reserves the right to 'check' (carry out diligence) on the other gala before consuming the agreement. It is thus assumed that this diligence is 'due' before consuming the settlement.