Thomas Firman of Selby, Yorkshire and of Dublin city inherited the estates of Richard Pierson. His son, John Firman, was "of Ballinderry and Arranhill, county Tipperary". John Firman's estate was valued at £600 in the mid 1770s (Kilboy Papers). John Firman's two sons were Thomas Pierson Firman of Firmount who married a Yorkshire heiress and Richard Flood Firman of Slevoir. The Firman family were related through marriage with the Smith family of Milford and the Biggs family of Castle Biggs.The representatives of Thomas P. Firman held an estate in the parishes of Borrisokane and Terryglass, barony of Lower Ormond, county Tipperary, in the mid 19th century. In May 1852 the Firmount estate, barony of Lower Ormond and the lands of Grange and Clohane, barony of Eliogarty, over 1,300 acres in total, were advertised for sale and appear to have been bought by the Hickies and Delanys. In July 1862 the estate of the administrator of William Firman,, deceased, at Muckloon "now called Firmount", 85 acres in the barony of Lower Ormond, was advertised for sale.
The Irish Times reports its purchase in trust for Samuel D. Biggs.