帮你找到的：The term skeleton key is also often used to describe lever lock keys. This usage perhaps stems from such keys' resemblance to a skeletal figure, with the circle at top circumscribing the triangle at one-third the vertical length, resembling a stylized skull.
因为最初的万能钥匙其实不是单独的一把，而是钥匙上面挂着尽可能多的附件，好在一个不好使的情况下用另一个开锁，然后整体看上去非常像“骷髅”的形状，因此而得名。
希望可以帮到你~
