Funnily, and ironically, enough, as a native French speaker, I would never translate "ce ne sont pas mes oignons" (litt. "those are not my onions") as "it's not my cup of tea". To me, it actually means "it's none of my business".
There are many queer things in (past) translations, it is funny when they stick.
In Italian we have the expression "la bellezza dell'asino" (which is "the beauty of the donkey" and it means - nonsensically - the kind of beauty/freshness that only young people can have and that will vanish with the passing of time).
It derives from the combination of a typo with a "faithful" translation from French, the original “la beauté de l’âge” had been printed as “la beauté de l’âne” and translated directly to "la bellezza dell'asino".
I’m glad you said that because I thought I knew that ‘mêle-toi de tes oignons’ meant ´mind your own business!’ and I was doubting myself after reading that.
