To take the wind out of someone's argument or leave them stunned and surprised at the action you took. Usually used in the past tense when describing the situation to a third party.
"I'm going to give you all my work to do, that'll soften your cough"
"I gotJimmy back so good, that'll soften his cough"
When smoking marijuana and someone coughs you can say "no cough no stone" (as in "no pain no gain"). It means the coughing weedsmoker will get stoned anyway and need not worry.
I had to cough badly when she handed me the spliff, but she smiled and said "no cough no stone".