Patients with this condition are said to smell like decomposing fish, because their bodies don't break down a compound called trimethylamine, which emits the je ne sais quoi of fishiness.
That phrase is borrowed from the French for, I don't know what, but now refers to that little somethin' somethin' that's indefinable or je ne sais quoi.
That's not to say that they're entirely untranslatable, because we can do our best approximation of them, but there's that intuition that a non-native speaker wouldn't have that, je ne sais quoi, if you will.
这并不说它们完全不可译,因为我们可以对它们进行最好近似,但有一种直觉, 非母语人士不会有这种感觉,je ne sais quoi, 如果你愿意话。
Second, Apple relied on contract manufacturers for its iPhone from the beginning, making it impossible to tell how much of its outperformance is down to this strategy rather than some other commercial je ne sais quoi.