From Britain or Brittany
A modern phonetic spelling of Brittany, which originally referred to people from the region of Brittany in France or the island of Britain. It gained immense popularity in the late 20th century before evolving into various creative respellings.
Less common today
Brytni isn't in the latest US Top 1000. It last peaked at #8,027 in 1999.
US births per 5-year period, 1990βpresent (SSA data).