Could you please tell me an equivalent of "all this ... business" to understand the precise meaning of this expression in the following excerpt from the chapter Seven of The Great Gatsby?
“That’s a great expression of yours, isn’t it?” said Tom sharply.
“All this ‘old sport’ business. Where’d you pick that up?”
It is in chapter seven where Tom beings to demonstrate his boorish tendencies towards Gatsby. It is becoming clear that Tom feels that Gatsby is trying to endear himself. Tom sees Gatsby as "new money" and uses it as a wedge to try to denigrate him. This denigration not only serves to keep Gatsby apart from the protected circle of wealth that Tom, Daisy, and Jordan enjoy, but also to make him lose his allure in Daisy's eyes. Part of Gatsby's allure has been the mystery about his past, and this is where Tom seeks to strike. He does this with his "Oxford, New Mexico" to denigrate the claims of Gatsby's lineage of class.
The next step in this process is for him to attack his style of speech. In suggesting to Gatsby that his way of speech is fraudulent, Tom makes the comment "All this ‘old sport’ business. Where’d you pick that up?” It is his way of saying that the way Gatsby speaks is phony and contrived. An equivalent way of expressing it would be for Tom to have said, "Your accent" or "The way you speak. Where's you pick that up?" The idea of "picking up" language is Tom's way fo saying that Gatsby is a phony, someone who is not real and authentic, but rather contrived. The reduction of the way in which Gatsby speaks as "business" and something that is "picked up" is a way to illuminate what Tom sees as Gatsby's phoniness. In this, Tom is able to assert power over Gatsby.