The English expression “That’s another kettle of fish.” has a French equivalent expression.
This idiom is used when we want to say that something is different from what we were just talking about. For example, if we were discussing the difficulty of learning a new language and then switched to talking about the challenges of starting a new job, we might say “that’s another kettle of fish.” It is believed that the expression comes from Scottish dialect, where “kettle” meant “matter” or “affair.”
In French, the equivalent expression is “C’est un autre paire de manches,” which translates to “That’s another pair of sleeves.” This expression is used in the same way as the English idiom, to describe a situation that is different from what was just discussed. The origin of this expression is also unclear, but it is believed to come from the idea of wearing different sleeves to match different outfits.