"One of the founders is a plonker!"
Many moons ago, the two founders who at the time were; young, naive and care free, didn't know much about business at all. They thought their start-up business might only last 2 or 3 months, but their mentally was, "let's give it a go and see what happens."
The founders had to make an important decision, they needed a name! One of the founders was day dreaming and suddenly thought about cheese, and then randomly about a different type of cheese, maybe Rubber Cheese.... yes, that sounds good... Rubber Cheese. Let's go with that!
Little did they know that they'd still be around 12 years later and have to keep the name that randomly popped into the founders / plonkers head!