There were times when people were warned that not everyone would understand this straight away. It was sometimes suggested that it would be sensible to include the label ‘menu’.
That’s still perfectly fine to do, but as is often the case: after a few years of use, most visitors do know what this icon means and what it does: it opens the navigation menu. When that happens, you can speak of a (user) behaviour pattern: the public knows how to use it.
