I had a conversation with Ernie Ball ( I worked there 1998-2001) and he said in 1962, session players were coming into his shop and buying a set of Fender strings with a .013' on the high E, and one .009 Banjo String. He thought this was odd - so he would talk to the customer who explained that several LA session players would use the .009 Banjo String on the Hi E, and throw away the Fender set's low E.
"Super Slinky" was named by Ernie Ball's kids who worked in the family garage repackaging Fender Strings for the first year - named after a popular 1960s spring toy that was heavily marketed on TV. "Slinky" was a household name, and easily described the low tension elasticity of the Ernie Ball "Super Slinky" string set.
So heading into a music store in 1966 , it was far easier to just say "I'll have a set of "Super Slinky Strings".
And Ernie Ball invented the idea of selling individual strings and allowing the customer to build a "Custom Gauge" set.
The first item the company made were those hardwood string holders - you still see them in use at older music stores.
http://www.ernieball.com/history