This feature is new in the Software Express pilot program. This feature is included in the Solaris 10 3/05 release.
For login accounts that are defined in local files, a password history of up to 26 previously changed passwords can be enabled. When a user changes a password, the attempt fails if the new password matches one of the passwords in the history. Also, login name checking can be disabled.
See the passwd(1) man page for more information.