Albion, you might be interested in a blog post I wrote comparing various cine lenses from the 20s to modern times, specifically looking at the out-of-focus characteristics:
There's a lot of internet conjecture about the causes of swirling bokeh, I can't say I have a definitive answer either, but the images in my post are interesting to study. I don't think the effect is limited to or caused by a particular lens family like Double Gauss, I'm pretty sure some C mount triplets had it too, but maybe the Double Gauss line is easily susceptible. Then again, you don't find it in modern Double Gauss derivatives like Zeiss Planars, which are used in many Zeiss cine lenses.
I think it's probably partly due to iris vignetting, which causes cat's eye shaped highlights that create the sense of ovals circling around the image centre. But mainly I think it's an astigmatic effect, where radial and tangential lines focus at different planes. These are normally somewhat corrected to meet in the plane (or curvature) of focus but depending on the design the out-of-focus areas may be much less blurred in the tangential direction, leading to a sense of circular motion. This correction is intimately linked with field curvature.
In the Alexa stills part of my blog post (the shots of a Bolex against a window) the Meyer Primoplan lens (from the 30s) shows the most obvious swirly bokeh, and you can see from the de-focussed projection image of that lens that the tangential lines are less blurred than the radial ones. Other lenses tend to blur in different ways. Some of the other older lenses, like the Schneider and the Speed Panchro, exhibit the cat's eye highlights, but don't seem as swirly as the Meyer. I haven't pulled apart a Primoplan to check, but from a Google search the Primoplan appears to be a Cooke Triplet derivative, not a Double Gauss.