The Oxford Advanced Learner`s Dictionary (http://oald8.oxfordlearnersdictionaries.com/dictionary/mad) states as follows:
mad: having a mind that does not work normally; mentally ill
In consequence no mad should mean normally working, mentally sane
According to Wikipedia (http://en.wikipedia.org/wiki/Nomad):
Nomad: is a member of a community of people who move from one place to another.