pour cold water on

Also, throw cold water on. Discourage or deter, as in Cutting my year-end bonus poured cold water on my loyalty to the company, or Hearing about the outbreak of cholera threw cold water on our plans to visit Bolivia. This term, with its image of putting out a fire with water, at one time meant “defame” or “slander”; the modern meaning dates from about 1800.

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