U+1D99 Latin Small Letter U with Retroflex Hook

The Wikipedia has the following information about this codepoint:

In typesetting, the hook or tail is a diacritic mark attached to letters in many alphabets. In shape it looks like a hook and it can be attached below as a descender, on top as an ascender and sometimes to the side. The orientation of the hook can change its meaning: when it is below and curls to the left it can be interpreted as a palatal hook, and when it curls to the right is called hook tail or tail and can be interpreted as a retroflex hook. It should not be mistaken with the hook above, a diacritical mark used in Vietnamese, or the rhotic hook, used in the International Phonetic Alphabet.

Letter ⟨Z⟩ with tophook - became letter ⟨⟩.

Letter ⟨X⟩ with two high hooks - became letter ⟨⟩.