LORELAI: Her lineage includes Cocker Spaniel, Golden Retriever, Bouvier des Flandres –
RORY: Gesundheit.
Gesundheit means “health” in German, and is used as a response to someone sneezing in the same way as “Bless you”, although “Gesundheit” is less common in North America.
Rory is suggesting that Bouvier des Flandres sounds like a sneeze.
The Annotated Gilmore Girls 