At October 10 the earliest of the Irish calendars, the late eighth-/early ninth-century Martyrology of Tallaght, records the name Sillani abbatis. The name of Sillan the abbot is also recorded in the twelfth-century Martyrology of Gorman as well as in the seventeenth-century Martyrology of Donegal. No further details of the saint, his locality or his monastery have survived. Curiously, Eoin Neeson in his compendium of Irish saints makes no mention of the abbot on this day but instead records 'Siollan, a holy woman of Inchigeela, County Cork'. I can't find any other evidence for this holy woman, all of the other saints with the name Siollan or Sillan I've come across are male, the most famous perhaps being Saint Sillan of Bangor, commemorated on February 28.