Meanings
From Middle English God blesse you, God blisse you.
How to pronounce "bless you":
AU
Short for (may) God bless you: said as a short prayer for the recipient.
Said to someone who has just sneezed, as a polite remark.
Used to express non-understanding of someone who has just used an unusual or foreign word or phrase (as if to imply that it sounds like a sneeze).