Wikipedia states that your interpretation is not 100% certain. It says that there is also believed to mean "vast place," which is not in dispute.

https://en.wikipedia.org/wiki/Namib#Etymology

So, a vast nothing

Where are you getting the gloss? Wiktionary has a definition "wasteland", but also derives it etymologically from a verb meaning "walk". Is there an element that means "nothing"?

I was told it by my driver when I visited the desert during a trip to Angola. Where he got it from? No idea.

This reminds me of the dead sea, it's far from dead, there are life forms in it. It's called the dead sea in Arabic as well (maybe this is the source of the name? Don't quote me on this one)