It's a pseudonym, suggesting India and the Indian Ocean.
"Banyan, a column on Asian politics, is named after the banyan tree under which Gujarati merchants would conduct business."
"All writers at The Economist are anonymous. And yet our columns—such as Bagehot, Lexington, Schumpeter—have fairly unusual names to distinguish them. Where do the names come from? Newspapers and magazines have a history of journalists using pseudonyms, whether for gossip writers or undercover investigative reporters. The use of names in The Economist indicates that a column is (nearly always) written by the same journalist from one week to the next."
According to Wikipedia, "'Banyan merchants' is an expression used widely in the Indian Ocean trade to refer to Indian merchants who are clearly distinguished from others, by their clothing, by their religious and cultural dietary choices, and by the manner in which they conduct trade."
Clearly, The Economist likes names beginning with "B"--and they like names of trees because in addition to "Banyan" they use "Baobab" and "Buttonwood."
(I would have known "Buttonwood" without looking it up. The ancestor of the New York Stock Exchange was created by an agreement supposedly signed under a buttonwood tree on Wall Street.)