I had never heard of the third meaning that you wrote about, Bingley, and have always pronounced it (wrongly, as I now find) as DOW-S, in both of the other contexts. But here's what my M-W says on the subject of douse:

DOUSE or DOWSE: (DOW-S)
1. to plunge into water or the like
2. to splash or throw water or other liquid on
3. to extingusish
4.(informal) to remove; doff
5.(Naut):
a) to lower or take in a sail or a mast
b) to slacken a line suddenly
c) to stow quickly
6.(Brit) a stroke or a blow

DOWSE (DOW-Z)
to search for underground supplies of water, metal by the use of a divining rod

And Bingley, you brought up a most beautiful word, Firdaus (FIR-DHAWS). The AW has to be dragged out to give it an 'OH' lilt. It is a Persian word which loosely tranlates into empyrean or paradise. (??Paradise and Firdaus appear to share a common root). It is used to acknowledge the gift of something so unique that God could only have crafted it when he had nothing else on his mind; thereby implying that, God made it at his leisure. It's also a somewhat common name for girls in Persia and northern parts of India.