in phpBB3/language/en/viewtopic.php we have:
'FULL_EDITOR' => 'Full Editor & Preview',

For a long time i have been think why this button needs such a long name.
I think just "Full Editor" will be better and more simple and quick to read.
And yes the page does have preview, but it also have attachments and other stuff.
I think its better to just keep it simple and not have to mention secondary stuff like preview that the user might not even be interesting it using.