It is derived from the initial form of the Arabic letter hāʾ, ⟨هـ⟩.

[citation needed] In the Unicode text-encoding standard, this letter is called "Abkhazian Ha".

[1] Its form bears some similarities to the Greek letter Theta (Θ θ/ϑ).

In English, O-hook is commonly romanized using the Latin letter O with dot below (Ọ ọ) but its ISO 9 transliteration is the Latin letter O with grave accent (Ò ò).

O-hook is used in the alphabet of the Abkhaz language where it represents the labial-palatal approximant /ɥ/, the sound of ⟨ui⟩ in French "huit" ([ɥi]).