Where the shape comes from
A standing figure with one leg bent under it, the traditional picture of lameness — a body still upright but favoring one side. Very few common characters carry it today; it survives mainly as a dictionary classifier for a handful of rare words describing infirmity or a crooked stance, its everyday work in the modern language long since taken over by other, unrelated characters that merely resemble it.
汉字 filed under 尢
No published character on HSK Guide is filed under this radical yet. 汉字库.