Update Feb 2018:
Thanks to @JamesNisbet for pointing this out in the comments.
According to the Chrome team, autocomplete="off" and autocomplete="false" will be ignored moving forward. This is not a temporary regression in Chrome.
Chrome will attempt to autofill any form fields that follow the WHATWG standard on autocomplete. With one exception, they ignore "off" and "false" values.
In summary, to disable autofill, use the autocomplete attribute with a value that is not on the WHATWG list.
Make your case why you think autocomplete="off" should not be ignored by Chrome in this Chromium thread.
Looks like a possible regression in Chrome 63. In Chrome's original autofill documentation:
In the past, many developers would add autocomplete="off" to their form fields to prevent the browser from performing any kind of autocomplete functionality. While Chrome will still respect this tag for autocomplete data, it will not respect it for autofill data. So when should you use autocomplete="off"? One example is when you've implemented your own version of autocomplete for search.
https://developers.google.com/web/updates/2015/06/checkout-faster-with-autofill
They do make a distinction between autocomplete and autofill, although it's not clear they are different.
Chrome, Safari, and Edge are all attempting to implement autofill but there is no clear standard. They look at the name attribute rather than an explicit, standardized attribute.
For now autocomplete="something-new"
is a good workaround, although syntactically it makes no sense. This seems to work because the browser can't understand it.