I don't even know where to begin, is the language is even matter or it make no differences?
The question is as follow: Open a random English book, pick up $x$ random words. Then pick up another word. What are the chances that the last word you picked will come before the all the other words you picked in alphabetic order?
Assuming no words can be repeated in the list, the answer is $\frac{1}{21}$. Each of the $21$ chosen words is just as likely as any other to be the first lexicographically.
If you want to be technical, there is a very, very small chance that two of the chosen 21 words are the same word, and furthermore are (depending on how you look at it) both first. This would make the chance ever so slightly higher than $\frac{1}{21}$, by an amount dependent on the word frequencies in the source.