Pwgen is a small, powerful, GPL'ed password generator.

This   version   of   pwgen    was    written    by    Theodore    Ts'o
<tytso@alum.mit.edu>. It is modelled after a program originally written
by Brandon S. Allbery, and then later extensively modified by Olaf Titz,
Jim Lynch, and others. It was  rewritten  from scratch by Theodore Ts'o
because  the original program  was somewhat of a hack, and thus hard to
maintain, and because the licensing status of the program was unclear.

WWW: https://sourceforge.net/projects/pwgen/