U+1DF0A Latin Letter Retroflex Click with Retroflex Hook

The Wikipedia has the following information about this codepoint:

The retroflex clicks are a family of click consonants known only from the Central ǃKung language or dialect of Namibia. They are sub-apical retroflex and should not be confused with the more widespread postalveolar clicks, which are sometimes mistakenly called "retroflex" (for example in Unicode) due to their concave tongue shape.

The 'implicit' symbol in the International Phonetic Alphabet that represents the forward articulation of these sounds is ⟨𝼊⟩. However, usage is rare. In the literature, retroflex clicks are typically written with the ad hoc digraph ⟨‼⟩, the convention since Doke identified them as retroflex in 1925. (Doke's proposed symbol, ⟨ψ⟩, did not catch on, though it has IPA support for historical transcription, nor did Vedder's and Anders' ⟨⦀⟩. For a while Amanda Miller, who noted a lateral fricated release (as had Vedder), transcribed them ⟨ǃ𐞷⟩.)

Retroflex clicks are extraordinarily rare. True retroflex clicks occur in at least some dialects of Central ǃKung. They are reconstructed for the Proto-Kxʼa language and tentatively for Proto-Khoe–Kwadi. The Damin ritual jargon of Australia may have had a voiced nasal retroflex click, transcribed by Hale & Nash as ⟨rn!⟩, though it's not known if it was phonemically distinct. However, Damin clicks presumably reflected the consonant articulations of Lardil, in which the "retroflex" consonants are retracted apical alveolar rather than true retroflex, so it is likely that the Damin distinction could be described as post-alveolar apical [ᵑǃ̠] (⟨rn!⟩) vs a more fronted apical [ᵑǃ̪] (⟨n!⟩).

Basic retroflex clicks are: