down for the count - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Defeated, finished, doomed, as in I doubt if he'll ever leave the hospital; his illness really has him down for the count. This expression alludes to the losing boxer, unable to get to his feet before the umpire has counted to ten (the count). [1920s]