The name 5 Beans Bookkeeping was taken from an old English saying "Knowing how many beans make 5", meaning somebody who knows what they're talking about.

The saying even has an accompanying rhyme which was the source of much discussion on a John Peel radio show in the early 90s. Mr Peel was very surprised to discover not only how many people were familiar with phrase, but also just how many variations of the rhyme there were among his listeners. 

Here is the version I know...

A bean and a half

Half a bean

Half a bean

A bean and a half

and a bean

That's how many beans make 5!