Not one's concern, as in
How much I earn is none of your business. This expression employs
business in the sense of "one's affairs," a usage dating from about 1600. (Also see
mind one's own business.) A slangy, jocular variant from about 1930 is
none of one's beeswax. The related verb phrase
have no business is used to indicate that one should not meddle or interfere, as in
He has no business discussing the will with outsiders.