Polnoon Castle, an ancient castle in Eaglesham parish, Renfrewshire, near a head-stream of White Cart Water, 5 miles S by E of Busby. It was built with the ransom of Harry Hotspur, whom Sir John Montgomerie had taken prisoner at Otterburn (1388); and it long was a chief seat of the Eglinton family; but it is now represented by only a few smooth mounds of rubbish.Ord. Sur., sh. 22, 1865.

(F.H. Groome, Ordnance Gazetteer of Scotland (1882-4); © 2004 Gazetteer for Scotland)