root@solaris:~ # passwd emerson
New Password:
passwd: Password in history list.Please try again
New Password:
According to this blog post Solaris 10 Password History, Solaris 10 implemented a new parameter (HISTORY) in /etc/default/passwd. This parameter keeps all the used password to prevent password recycling.
You can set to a smaller number if you wish
root@solaris:~ # vi /etc/default/passwd
HISTORY=1