wheel within a wheel

From the Bible, Book of Ezekiel, 1:16.

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wheel within a wheel (plural wheels within wheels)

1. (idiomatic, often in the plural) A complication of circumstances, motives, etc.
   • 1933, P. G. Wodehouse, Heavy Weather‎:

     The fact is, there’s something I rather wanted to call to your attention. You don’t know it, but for private and personal reasons I particularly want to hold this Tiny Tots job for a year. There are wheels within wheels. It’s a sort of bet, as a matter of fact. Have you ever met a girl called Gertrude Butterwick?… However, it’s a long story and I won’t bother you with it now. But you can take it from me that there definitely are wheels within wheels and unless I continue in your employment, till somewhere around the middle of next June, my life will be a blank and all my hopes and dreams shattered.

• “wheels within wheels”, in OneLook Dictionary Search.