Origin of "Egyptian night"?

Posted by Tennis Smith on November 22, 2004

Hi,

I've often wondered what it meant in phrases like:
"It seems to me, sunk in my Egyptian night, that the man who fails to do this in the United States to-day is a man who is somehow stupid-- maybe not on the surface, but certainly deep down." - HL Mencken

Anyone know?

Thanks,

-Tennis