1914, from German Gesundheit, literally "health!" Also in toast auf ihre Gesundheit "to your health" (see sound (adj.)). Lithuanian aciu, echoic of the sound of a sneeze, has come to mean "good luck, God bless you." See also God.
German for “good health.” Like the English phrase “Bless you,” it is conventionally said to someone who has just sneezed. This reflects the superstition that a sneeze can cause the soul to fly out of the body; saying the phrase prevents this from happening.