[T]hey are troubled with the je-ne-scay-quoy, that faign themselves sick out of niceness but know not where their own grief lies, or what ayls them. [Thomas Blount, "Glossographia," 1656]来自法语je ne sais quoi,即I do not know what,来自je,我，词源同I,ne,不，词源同not,sais,知道，词源同savvy,quoi,什么，词源同what,quality.引申词义妙不可言，难以言表。
该词的英语词源请访问趣词词源英文版：je ne sais quoi 词源，je ne sais quoi 含义。