when a chicken somehow gets in your pants and you attempt to choke it but miss and start choking your dick. it happens to almost all males who live on or near farms that have chickens.
male 1: hey don't you be choking my chicken man male 2; what chicken?
male 1; that chicken in your pants.
male 2; time to begin choking the chicken
well there was this chicken named mike who lived a normal chicken life untill he had his head cut off. Despite the decapitation mike was able to lead a pretty normal life for 18 months untill he finally choked to death.
Although tragic i think it may explain the saying.