go south

• head south, move south, turn south, see Usage notes below

(become worse): The origin is unclear. Common belief attributes it to the standard orientation of maps, where south is the downwards direction. Alternatively, it could stem from a euphemism used by some Native Americans for dying.[1]

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go south (third-person singular simple present goes south, present participle going south, simple past went south, past participle gone south)

1. (idiomatic) To become unfavorable; to decrease; to take a turn for the worse.

   I should have walked away from the casino when my luck went south, but I stayed and ended up in the hole.

   • 1967, Bill Sparks, Wild Weasel mission 5 November 1967

     I still had 5 miles (8 km) or so to go to cross the river when all of the controls went south. The bird pitched up, shuddered, rolled right like it was going to spin […]

   Synonym: go left

2. To make an escape; to disappear.
   • 1929, Peter B. Kyne, The Parson of Panamint and Other Stories, page 197:

     He won! A disbeliever, from childhood, in the frequency of miracles, he gathered up seven hundred and forty dollars and "went south" with it.

   • 2004, Cory Doctorow, Microsoft Research DRM talk:

     […] she decided to tape the DVD off to VHS and give that to the kids -- that way she could make a fresh VHS copy when the first one went south.

3. (slang) To give somebody oral sex.
4. (poker slang) To rathole: to take chips off the table in a cash game without exiting the game completely, especially with the intention of limiting losses.

This idiom is constructed with a variety of terms, all consisting of a verb indicating movement and a direction indicating the movement is to the south (southerly, southward, etc.) The exact construction may be modified to fit the circumstances.

He was unconcerned that his health might turn south.

Yesterday the stock market moved south, ending up on a loss for the day.

Afterward, when company profits had ventured a bit too far southward, the CFO began to get nervous.