Farrell Family Tree Road Block

Hello. I have a roadblock in my Farrell Family Tree.  My Great-great-great Grandfather was Michael Farrell, born in Longford in 1818, emigrated to the US in 1838, eventually settling in southwest Pennsylvania/West Virginia where died in the early 1900s. There is some decent history from his time in the US, but I don’t find much history from his days in Ireland. There was a book called the history of Fayetteville County (Pennsylvania) where is said Michael’s father was William.  It states that William was born in Longford in 1781 and “ lived and died in his native land where he left issue.”  I understand that “issue” means that he had children and descendants.

now, I understand that there are no shortage of Farrells in Longford and I’m also certain there are many more than just one William.

If anybody could provide some insight into William and/or young Michael, that would be appreciated.