Gollum has his own category of words, such as “iss” and “preciouss”, which would have been knocked out when the Python script eliminated The Ten Thousand most common words but for his speech impediment.  I have just crossed out another one which I believe deserves special mention.

Dursn’t is not simply the negative form of dare.  Google’s Ngram function reports that “dursn’t” and “dassn’t” were used in roughly the same proportion from 1800 until now – less than 20 times as frequently as “daren’t”.  Gollum uses a less common form, enhancing his hermit reputation.

• 05.124 But we dursn’t go in,
• 05.124 no we dursn’t.

I will find out if any of my local libraries subscribe to the OED on line in order to better research the antiquity of words.  If not, I will be taking advantage in May of the OED’s free 30 day trial – more answers then.

OED update!  The word history of “dare” is a fascinating rabbit hole and I highly recommend it as summer reading.  The letter S plays a merry game of hide-and-seek in this word.  “Durst” is given as a past tense, co-equal with “dared” and listed first which I believe means that it is attested as older – it’s also tagged as colloquial in some uses.  Is Gollum using it in the present tense?