When an English speaker talks about someone being “down for the count,” he or she is most often referring to a situation where the subject has lost a struggle or otherwise failed. The idiom is a sports metaphor that expresses a negative outcome for whoever or whatever the speaker is referencing. This phrase is also used in show business, for example in the names of performance artists and musical bands.
Many people trace the origin of this phrase back to the 1920s. Some see it as an American idiom overall, although the use of the phrase may be common and other English-speaking societies. A similar phrase, “out for the count” dates back almost as far. This alternate phrase refers more to a loss of consciousness, hence the preposition “out” rather than “down.”
The alternate phrases “down for the count” and “out for the count” both reference the same types of contact sports. Most prominently, many people associate these idioms with the sport of boxing. In boxing, a “ten count” gives the player who has fallen to the ground a chance to get up and continue fighting. If that person stays down through the count, he or she has not been able to recover, and has lost the fight.
Some similar phrases are sometimes used for this kind of situation. For instance, someone who is using the phrase idiomatically might also call something a “TKO.” The acronym stands for a total knockout, which often results in the player being “out for the count.” Speakers can also use the simpler “KO” which stands for knockout as a verb, for instance, by saying “the high tax rate KO’d the project.”
It’s important to distinguish these idioms from the phrase “down and out.” Although “down and out” might have originally been a sports metaphor, it is much more associated with general bad luck and failure than with an immediate failure, such as “down for the count” implies. Using the phrase “down for the count” implies that the failed party has lost the immediate battle, but may be able to recover soon and retry the failed scenario.