What is this grapheme still in use as a letter in some languages, including Danish, Norwegian, and Icelandic that the Old English Latin alphabet had?
Old English Latin alphabet The Old English Latin alphabet—though it had no standard orthography—generally consisted of 24 letters, and was used for writing Old English from the 9th to the 12th centuries. Of these letters, 20 were directly adopted from the Latin alphabet, two were modified Latin letters (Æ, Ð), and two developed from the runic alphabet (Ƿ, Þ). The letters K, Q and Z were not in the spelling of native English words.
Omega (Cyrillic) Omega (Ѡ ѡ or Ѡ ѡ; italics: "Ѡ w" or "Ѡ ѡ") is a letter used in the early Cyrillic alphabet. Its name and form are derived from the Greek letter Omega (Ω ω).