I wanted to make one quick analogy with parliamentary procedure. There are some parliaments of the world where they have codified specific words that you cannot use in the given chamber at any time.
We in the Parliament of Canada, for instance, have not gone down that route. There are codified explanations contained in the parliamentary procedure and practice of the Standing Orders and like that, but there is no list of words you cannot ever use. It's up to the Speaker to determine on a given day whether the word is non-parliamentary. You could have an instance where one day a word creates a disturbance, and the Speaker will probably get a member to withdraw it. Another day if it's a bit quieter in the House, the same word can be used by a member, and it's not deemed to be non-parliamentarian. That's where the flexibility issue kicks in.