Bean, this was Gurunet's word of the day (aside: no, I haven't been straying: Gurunet opens automatically whenever I turn on my computer, and sometimes I notice their word), and it made me think of you:
hadal
ha¡¤dal (h¨¡d'l) 
adj.
Of or relating to the deepest regions of the ocean, below about 6,000 meters (20,000 feet). 
[French, from Had¨¨s, Hades, from Greek Haid¨¥s.]


I guess you already knew this word? (Having previewed the post: once again, the diacritical characters aren't transferred correctly, despite my using [pre].)