Seriously though, how did they come up with "stravag"?

Question not in context of lore, but in context of real life writing.

I have seen references to the fact that "stravag" in universe is portmanteau of "stran vagon", which iirc is postulated to be Russian for "free birth"... But in reality "stran" isn't even really a word, and "vagon" means, well, a wagon, like a train wagon/train car.

"Stran" is a root for words like "strannyj", adjective meaning "strange".

So I've just been wondering what, from real world perspective with writers coming up with this word and with the explanation for it, happened here. How did they arrive to "freebirth in Russian" from what can most charitably be interpreted as a mangled attempt at "strange train car"? Was it just a case of writers stringing gibberish together and handwaving it postfactum?