mokita
"Mokita" means "the truth everyone knows but no one talks about," according to Wendalyn at Mavens' Word of the Day.
Wendalyn adds that the word apparently "comes from the Kilivila language spoken on Kiriwina, the largest of the Trobriand Islands, part of Papua New Guinea."
It's still not in dictionaries, but it appears to be gaining wider use in political circles.
It's not clear to me whether it's used to refer to ordinary things that are so obvious that nobody bothers talking about them, or only things that are too sensitive to discuss.