Q.
Where did the phrase ‘no truck’ originate? As in: “I have no truck with back room business deals.”

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A.
I want or have no truck with X. That is, I want no part of this. I refuse to be involved.

How on earth are trucks relevant here? What is the basis of this idiom?

This is certainly not one of the easier phrases to unriddle. The most commonly accepted theory is that the ‘truck’ here originated with the French word ‘troque’ meaning an exchange, barter, or swap. So, in the negative sense, I want no part of this deal.

We see the phrase in one of  Agatha Christie’s short stories: ‘The Thumb Mark of St. Peter’, Chapter 6 in ‘The Thirteen Problems.’

“Who is your doctor?” I asked.
“Dr. Rawlinson.”
“I knew him by sight. Mabel had pointed him out to me the other day. To put it in perfectly plain language he was what I would describe as an old dodderer. I have had too much experience of life to believe in the infallibility of doctors. Some of them are clever men, and some of them are not, and half the time the best of them don’t know what is the matter with you. I have no truck with doctors and their medicines myself.”
“I thought things over, and then I put my bonnet on and went to call on Dr. Rawlinson…”

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