As raised in WordPress/wordpress.org#358 (comment) I've been using 'Recovery code' in text, but wporg-two-factor uses Backup Codes.

Upstream in the two-factor plugin, they were renamed to Recovery Codes (albeit, by me) in WordPress/two-factor#521

That upstream rename has flowed through to the login screen:

These are not at all a "backup" (a copy of..) nor are they intended on active use by the holder, rather, it's intended on being an emergency-access or "recover your account access" type scenario. At least in my mind. It may be better to call them Emergency Account Access token even.

We should just standardise on one or the other, whatever that may be.