Description:
As said at:
  http://dev.mysql.com/doc/mysql/en/debugging-server.html
" The command mysqladmin debug will dump some information about locks in use, used memory
and query usage to the MySQL log file. "
But in help message of mysqladmin there is no any note about this command. Also  at:
  http://dev.mysql.com/doc/mysql/en/mysqladmin.html
I didn't found an explanation of it. --debug - not the same as debug command, but
it is not clear from mysqladmin manual page.

How to repeat:
[gleb@toyou mysql-debug-4.1.9-pc-linux-gnu-i686]$ ./bin/mysqladmin --defaults-file=my.cnf
-u root debug
[gleb@toyou mysql-debug-4.1.9-pc-linux-gnu-i686]$
[gleb@toyou mysql-debug-4.1.9-pc-linux-gnu-i686]$ ./bin/mysqladmin --help |grep debug
  -#, --debug[=name]  Output debug log. Often this is 'd:t:o,filename'.
[gleb@toyou mysql-debug-4.1.9-pc-linux-gnu-i686]$

Thank you for the bug report. Verified on latest BK source.

Pushed to 4.1.

Mentioned in 4.1.10 change notes.

I also added the debug command description to the
mysqladmin section in the manual.