I wonder if there is any connection here, I know the spelling of Shahahan is different.
My great grandmother Honora (Rose) Shanihan was born about 1858 Tralee Ballymullen County Kerry Ireland She is the daughter of David Shanihan & Helena Grady. This information comes from her Marriage Certificate.
She married Daniel Horrigan on the 20 January 1881 in the Roman Catholic Church Toowoomba Queensland Australia. Daniel’s parents were listed as Patrick Horrigan & Johanna Kelleher. He was born in Kanturk County Cork Ireland.