1º_ Beyond its literal meaning, it is used with a specific sense by the chain that activated the old toilet flushes, which leads to the figurative sense "definitively get rid of what no longer serves", how excrement is eliminated. See "push the button" . 2º_ Another figurative use is to "leave someone with little room for maneuver, keep him tackled or controlled", associating the chain with the leash or the pretal that holds the beasts or attack dogs. This phrase appears more like "pulling him off the chain".
