Gee - I had to ask my mom about that one, Wayne. From my perpective, it's always been there.
The story really begins at the Standard Point family. These shapes were influenced by the Guilds we were modifying, but some customers complained about the large size (imagine that!). The Small Standard was in direct response to those customers and was influenced by the SG body shape.
This wouldn't have anything to do with a certain little MG bass, would it?