Known in those times as Knockaneen or Cnocán-an-éin-fínn, meaning 'the little hill of the white bird', the village once hosted an O'Brien castle that has since vanished from the landscape. The castle's existence is well documented; the 1654 Civil Survey noted that 'the walls of a Castle' stood on the land, which in 1640 belonged to Connor O'Brien of Knockane. Two sketches by Thomas Dineley from 1681 preserve the castle's appearance for posterity, though the structure itself has left no visible trace above ground.

The castle's fate was sealed during the turbulent period following the 1641 Rebellion, when the O'Brien lands were forfeited and subsequently granted to Lieutenant William Sheldon under the Act of Settlement. By 1904, when historian Berry conducted his survey, the castle had completely disappeared from view. Local memory, however, kept its location alive; elderly residents could still point out where it once stood behind Birdhill House. Martin Hassett of Birdhill provided a tantalising glimpse into the castle's last remains, recounting how his father had seen portions of the old foundations exposed during construction work on what became the stables under George Twiss's ownership.

Today, visitors to Birdhill will find no medieval stonework or romantic ruins to explore. The site where the O'Brien castle once commanded the landscape is now occupied by the stables of Birdhill House, its foundations buried beneath centuries of development. Yet the village's evocative name continues to echo its medieval past, when a castle stood on the little hill of the white bird, watching over the Tipperary countryside.