THE ANSWERS IS AS BELOW:
Hint: No, it is not that they all have at least 2 double letters.
(Thought I had the answer too, but I did not go far enough..)
The Real Answer:
In all of the words listed, if you take the first letter, place it at the end of the word, and then spell the new word backwards, it will be the same word.
Take the first letter, place it at the end of the word: ananab
Then spell the new word backwards: banana
Did you figure it out?