nwamd(1)
Because I didn't know my WIFI password from the top of my
head, I entered the wrong one when nwamd(1) was
asking for it. But it didn't ask again. So I wondered
where the passwords are stored.
After some google'ing I found the correct command:
# dladm show-secobj
Then I could delete the stored password with:
# dladm delete-secobj nwam-twisti-xx.xx.xx.xx.xx.xx
It seems dladm(1) is just a frontend for
text files. The passwords are actually stored in
/etc/dladm/secobj.conf.