The English idiom the World's second oldest profession
is used to refer to a number of professions.
One frequent use of the phrase is to refer to spies and spying
An explanation of this phrase is that it must be the second oldest profession because
it is mentioned in the Christian bible
Paul Reynolds, a writer with the BBC, noted: "Rahab, of course, was engaged in the oldest profession."
- "Joshua son of Nun sent two spies out from Shittim secretly with orders to reconnoitre the country. The two men came to Jericho and went to the house of a prostitute named Rahab..."
Other writers write about other professions as the world's second oldest profession without stating why they should be considered the second oldest profession.