peculiar institution
n.— «Alabama is now the fourth Southern state where modern-day lawmakers have apologized for slavery. In Mississippi, though, there has been no grand push to get an official acknowledgment of regret for what was once euphemistically called “the peculiar institution.”» —“Mississippi still not among the states apologizing for slavery” by Emily Wagster Pettus Sun Herald (Biloxi, Mississippi) May 28, 2007. (source: Double-Tongued Dictionary)