It's unused currently because jQuery provides a way to implement `undelegateEvents` in a single line. It may be best to think of it and `undelegate` as follows:

```javascript
{
    undelegateEvents: function() {
        this.undelegate('.delegateEvents' + this.cid);
        return this;
    },
    undelegate: function(eventName, selector, listener) {
        if (this.$el) this.$el.off(eventName, selector, listener);
    }
}
```

Though we're still going back and forth between namespaces( https://github.com/jashkenas/backbone/pull/3003#issuecomment-37402489 , https://github.com/jashkenas/backbone/pull/3003#issuecomment-3742415 ) . If we end up not using them any longer, I imagine `undelegateEvents` will more closely reflect `delegateEvents` and just loop over events, calling `undelegate` for each.