To rattle someone's chain (or cage)

The following text is from James Patterson's "Cross Justice" (from the Alex Cross series).
I don't understand the expression "rattle his chain" and "rattle away"near the bottom.
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“Naomi?" I called.
She turned and saw me, and her posture relaxed. “Alex!”
Grinning, she trotted over, threw her arms around me, and said quietly, “Thank God you’re here. This town is enough to drive me mad.”
"I came as soon as I could," I said. “Where’s Stefan?”
“Still in jail,” she said. “Judge’s refusing to set any kind of bail”
Matt was studying us –or, rather, me- intently.
“Is your friend the DA?” I asked quietly.
“Let me introduce you,” she said, “rattle his chain.”
“Rattle away,” I said.
Naomi walked me over to him, said, “Assistant district attorney Matthew Brady, this is my uncle and Stefan’s cousin Dr. Alex Cross…”

Did you try to find out the meaning before you asked us? I Googled "meaning of to rattle someone's chain" and got plenty of useful responses. Here's just one of them: https://www.wordsense.eu/rattle_someone's_chain/

emsr2d2 said:

Did you try to find out the meaning before you asked us? I Googled "meaning of to rattle someone's chain" and got plenty of useful responses. Here's just one of them: https://www.wordsense.eu/rattle_someone's_chain/

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Yes I did and I got the same results, but they just don't make much sense to me in that context.
I showed the text to an English friend of mine and he didn't see a clear meaning. I though it might be american slang, after all it's an american book.

rappiolla said:

Yes I did and I got the same results, but they just don't make much sense to me in that context.
I showed the text to an English friend of mine and he didn't see a clear meaning. I thought it might be American slang. After all it's an American book.

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I'm similarly puzzled. The suggestion "Rattle his chain" seems to encourage person A to provoke person B. And the response ("Rattle away") makes it stranger still. It seems to be something like a private joke. (Additional context might prove helpful.)

@Tarheel. I am no less than flabbergasted at your response. I believe, as I always have, that it is so common in AmE it's almost a cliche.

@Tarheel: some more text.

Naomi walked me over to him, said, “Assistant district attorney Matthew Brady, this is my uncle and Stefan’s cousin Dr. Alex Cross, formerly of the FBI’s Behavioral Science Unit and currently a special investigator with the Washington, DC, Metro Police.”

If Brady was impressed, he didn’t show it, and he shook my hand with little enthusiasm. “You’re here why, exactly?”

“My family and I have been through a rough time lately, so we’re on a little R and R to visit my roots and provide my cousin with some moral support,” I said.

“Well.” He sniffed and looked at Naomi. “I think you should be thinking plea bargain if you want to give Mr. Tate moral support.”

@probus

Could you please explain?

In addition to the explanation provided by @emsr2d2, I'd say it means tease or provoke.

I don't get the 'chain' idea but I imagine it's a corruption of the phrase rattle someone's cage. The metaphor is that you shake the bars of a cage of a locked up animal or person in order to provoke and agitate them. It seems to me that Naomi thinks that introducing Alex to the DA will in some way provoke them in such a similar way.

To me it's similar to "Let sleeping dogs lie". Dogs that may bite are often kept chained up and it would be unwise to disturb them by rattling their chain. It's a metaphor for that.

It sounds like they want to provoke him a bit before they do anything. Is Stefan an annoying character?

probus said:

@Tarheel. I am no less than flabbergasted at your response. I believe, as I always have, that it is so common in AmE it's almost a cliche.

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I certainly haven't haven't heard it often.

Maybe it's somewhat regional then. Would some of our other AmE speakers weigh in on this?

probus said:

Maybe it's somewhat regional then. Would some of our other AmE speakers weigh in on this?

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Perhaps not commonly used, but I believe, commonly understood across the U.S. .