Seanne is of Scottish origin, derived from the Gaelic 'Séarlas', which is itself a form of the Roman name 'Cecilius'. It means 'headstrong' or 'war-like'. The name gained popularity in Scotland and Ireland during the Middle Ages but has since become quite rare. Seanne was often used as a pet form of longer names like Cecilius, Cecil, or Ceallach.
"Seanne peaked in popularity during the mid-1960s with a notable decline thereafter, though it saw a slight resurgence at the turn of the century."