Answer: "eu" means "good", "daimon" means "spirit" or "soul". That is etymology. Eudaimonia means to live according to our own "daimon" (inner voice, inner spirit, soul etc.) or in other words to live authentically. According to Aristotle all that means to live a good life.
Explanation: This concept can be found in Nicomachean Ethics, which AristotleĀ“s work very important for psychology (for ex. humanistic psychology and psychotherapy: Carl Rogers or Maslow) or ethics.