It is form attribute autocomplete="off" and autocomplete="some string" for input field disabled

<form autocomplete="off">
    <input id="email" autocomplete="email" name="email" type="email">
</form>

So the problem is that autocomplete="off" is largely ignored in modern browsers - primarily due to password managers etc.. In your case autocomplete="disabled" is working because your browser doesn't recognize this value. So you may be happy that random value works for you as this solution sometimes doesn't work either.

Here are some other solutions to this problem: https://stackoverflow.com/questions/12374442/chrome-ignores-autocomplete-off"