call the shots

The Partnerを読んでいますが、いよいよ終わりに近くなってきました。
The first visitor to Mr. McDermott's temporary law offices was J. Murray Riddleton, Trudy's thoroughly defeated divorce lawyer. He sheepishly handed over a proposed settlement of property rights and child visitation. They discussed it over lunch. The terms of surrender were dictated by Patrick. And since he was now calling the shots, Sandy found numerous details to nitpick through. "This is a good first draft," he said repeatedly as he continued to mark it up with red ink. Riddleton took the thrashing like a pro. He argued every point, bitched about the amendments, but both lawyers knew the settlement would be changed to suit Patrick's whim. The DNA test and nude photos ruled supreme.
慣用句らしい "calling the shots" の意味が分からないので辞書を見ます。
・Collins Dictionary: The person who calls the shots is in a position to tell others what to do. ⇒ The directors call the shots and nothing happens without their say-so.
・Wiktionary:(idiomatic, chiefly US) To make the decisions; to be in charge; to give orders. You may know all about glassblowing, but here in the gym I call the shots.
語源が気になったので調べるとThe Word Detectiveに次の説明がありました。（以下は抜粋）
The real question, of course, is what all this shooting is about, and in the case of both "call the shots" and "call one's shots" the answer seems to be target shooting. In "calling one's shots," a target shooter (think Annie Oakley or the like) would announce in advance exactly where the target would be hit as a measure of his or her prowess. If someone else were "calling the shots," however, the shooter would be taking orders and hitting targets at that person's direction.
Note: Since the above column ran in newspapers I have been innundated with mail helpfully letting me know that "calling the shots" comes from the game of billiards or pool, wherein the player announces his shots in advance ("Eight ball in the side pocket" and so forth). Prior to researching the phrase, I, too, had assumed that it came from billiards, but the earliest citations I could find clearly refer to target shooting. That "calling the shots" occurs in billiards is clearly true. That it originated there is not.