At a factory in Burbank, CA, the young ice cream company experimented with hundreds of ice cream flavors that never made it to the public. This included Ketchup, "Grape Britain", and Lox and Bagels. This was years after they had come up with their first 31 flavors, but they kept the "31 flavors" slogan, and instead used it to mean that they will have a new flavor for every day of the month.
Irvine Robbins and his brother-in-law Burton Baskin had been running their own separate ice cream stores for a few years (Snowbird Ice Cream Store and Burton's Ice Cream, respectively) before merging. This was just after WWII; at the time, a store that only sells ice cream was a novel concept. By teaming up they started a sensation. The company changed its name to Baskin-Robbins in 1953. This was decided on a coin-flip, otherwise it would have been Robbins-Baskin!
You can read more about Baskin-Robbins in this Irvine Robbins obituary from the L.A. Times.