There are a couple of slang usages of beeswax, which are not related to one another.
The term, commonly used in the phrases mind your own beeswax or none of your beeswax, is an Americanism dating to 1934. It is simply an intentional malapropism for business.1
A more recent coinage is the use of beeswax as rhyming slang for income tax. It is also a play on the older rhyming slang bees and honey, meaning money. This British usage dates to the 1980s.2
1Historical Dictionary of American Slang, v. 1, A-G, edited by Jonathan Lighter (New York: Random House, 1994), 127-28.
2New Partridge Dictionary of Slang and Unconventional English, v. I & II, edited by Tom Dalzell and Terry Victor (Abingdon, UK: Routledge, 2006), 126.
Copyright 1997-2015, by David Wilton