go south

Deteriorate or decline, as in The stock market is headed south again. This expression is generally thought to allude to compasses and two-dimensional maps where north is up and south is down. However, among some Native Americans, the term was a euphemism for dying, and possibly this sense led to the present usage. [Slang; first half of 1900s] Also see go west.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.