The word "biorhythm" originates from two Greek words; "bios", meaning life and "rhythmos", meaning rhythm. The idea itself was developed by Wilhelm Fliess, a German otolaryngologist, who lived in the late nineteenth and the beginning of the twentieth centuries. He believed that our life is influenced by biological cycles, which affect the mental, physical, and emotional aspects.

Fliess derived three major biorhythmic cycles:

• Physical cycle
  Duration: 23 days
  Denotes:
  • Coordination
  • Strength
  • Well-being
• Emotional cycle
  Duration: 28 days
  Denotes:
  • Creativity
  • Sensitivity
  • Mood
  • Awareness
• Intellectual cycle
  Duration: 33 days
  Denotes:
  • Alertness
  • Analytical and logical abilities
  • Communication

The theory itself may be quite arguable, especially since it is considered pseudoscience by most of scientific public; however, it is scientific enough to, at least, serve for an example of a parallel data processing mechanism.