Apparently "double-gaited" means "bisexual," according to Chapman's American Slang.
I encountered it in a 1981 Elmore Leonard novel:
"[...] Yeah, I think he's fucking her. I think he'd be out of his fucking mind if he wasn't. Robbie Daniels doesn't strike me as being double-gaited or having any abnormal ideas what his dick is for," the detective said. "I mean outside the popular abnormal ideas that're getting more normal all the time."
--Elmore Leonard, Split Images, p. 15
The quote's a little odd; I would've assumed from that line that "double-gaited" meant gay, rather than bi. But apparently not.
Various online sources corroborate Chapman: Sexual Identity and Gender Identity Dictionary; Probert Encyclopaedia; Sex-Lexis Dictionary of Sexual Terms (though the database on that last one seems to have, um, gone down).
It derives from the term's use in horse-racing, of course. It's not clear to me whether the Polish/English dictionary that provides the term "dziwny" is referring to horse racing or sexual orientation.