It's the name of the main character. I have a children's version written in Standard Irish. I've enjoyed reading/translating it quite a bit. Neat stories..
Tá a fhios agam go bhfuil suim agat i bhfuaimniú na Gaeilge, a Ph. An bhfuil a fhios agat nach bhfuaimníter an litir 'd' san ainm "Séadna"? Is seanlitriú é sin -- an-ársa, actually. "Séanna" atá ceart i nGaeilge an lae inniu. Mar shampla: