The company was originally called Swallow Sidecar or "SS". Following WWII the "SS" obviously had a bad connotation in GB and elsewhere. So the company name was changed to "Jaguar" after one of there prior models.
By the '60's the meaning of "SS" apparently had been forgotten as Chevrolet used the "SS" for their Super Sport models of cars, even when they may not have been so "super".