You can change all language strings in CB using language overrides. See the below on how to add your own language overrides.
www.joomlapolis.com/blog/kyle/18701-language-overrides-have-arrived
You can also directly change the strings within CB > Field Management by editing the "Password" field and adjusting the field title as well as the titles for the other password fields under Parameters > Validation. There's also support for adjusting the profile edit title specifically under Parameters > Display using the "Profile Edit Display Title" parameter.