The Spanish word for fairy. This has snuck into English tales, but in doing so has become more vague in meaning -- in an English fairy tale a hada might be any supernatural humanoid with magical powers.
It comes from the Latin Fata (Fates) or Fatum (fate -- lit. "that which has been spoken"). English gets the word fate this same root.
HADA is also an acronym for High Availability Disk Array.