The name Ryann is a modern variation of the Irish name Ryan, which itself is derived from the ancient Irish Gaelic name Riaghan or Riain. This name is believed to have originated from the old Irish word "ri" meaning "king" or "illustrious", and the suffix "-an" which was a common diminutive form.

The name Ryan has been recorded as far back as the 7th century AD in ancient Irish annals and manuscripts. It was a popular name among the Irish nobility and ruling families during the medieval period. One of the earliest recorded bearers of the name was Riain, the son of Finnchu, who was an abbot and saint in the 7th century.

In the 12th century, a famous bearer of the name was Ruaidhri Ua Conchobair (Ryan O'Connor), who was the last High King of Ireland before the Norman invasion. He ruled from 1166 to 1198 AD and was known for his resistance against the Anglo-Norman invasion.

Another notable historical figure with the name Ryan was Riain of Inis Cathaigh (Ryan of Scattery Island), who was a renowned Irish poet and scholar of the 12th century. He wrote several religious works and poems that are still preserved in ancient Irish manuscripts.

In the 16th century, Hugh Ó Ruaidhín (Hugh O'Ryan) was an Irish chieftain and leader of the O'Ryan clan in County Tipperary. He was known for his support of the Irish Confederate Catholics during the Irish Confederate Wars against the English Parliament.

In the 19th century, Jeremiah O'Ryan was an Irish-American businessman and philanthropist who made a fortune in the shipping industry and founded the O'Ryan Charitable Trust in Boston, which still exists today.

The modern spelling variation "Ryann" emerged in the late 20th century as a feminized version of the traditional Irish name Ryan. While it retains its Irish roots and connection to the ancient Gaelic name Riaghan, the spelling "Ryann" is a more recent development, likely influenced by contemporary naming trends and preferences.