Checked a bit more for you
  
 There was one Registered Nightingale In 1815
  
 registered Downpatrick Aug 5th 1815
 John Nightingale Carrowreagh craigongauntlett
 Lord Baron Londonderry
 Names of Lives and Other Tenure
 alexander kennedy,william forde and alexander nightingale
  
 There are 3 Wills held by Proni
 Extracts of Wills
  
 Title:     
Forename:  Thomas    
Surname:  Nightingale    
Alt Surname:     
    Date Of Death:  03/03/1871    
Date Of Grant:  26/02/1872    
Effects:  Effects under £200    
Registry:  Belfast    
 
 
Full Abstract: 
The Will of Thomas Nightingale late of Carrowreagh County Down Farmer deceased who died 3 March 1871 at same place was proved at Belfast by the oaths of Robert Roddy and Thomas Nightingale both of Carrowreagh (Dundonald) aforesaid Farmers and George Nightingale of North-street Belfast County Antrim Boot and Shoe Maker the Executors 
 
Title:     
Forename:  George    
Surname:  Nightingale    
Alt Surname:     
    Date Of Death:  24/01/1879    
Date Of Grant:  17/02/1879    
Effects:  Effects under £200    
Registry:  Belfast    
 
 
Full Abstract: 
The Will of George Nightingale late of Ballymiscaw County Down Farmer deceased who died 24 January 1879 at same place was proved at Belfast by the oath of Matilda Nightingale of Ballymiscaw (Dundonald) Widow the sole Executrix 
Title:     
Forename:  John    
Surname:  Nightingale    
Alt Surname:     
    Date Of Death:  29/09/1909    
Date Of Grant:  09/08/1909    
Effects:  Effects £326 0s. 10d.    
Registry:  Belfast    
 
 
Full Abstract: 
Probate of the Will of John Nightingale late of Carrowreagh Dundonald County Down Farmer who died 29 September 1909 granted at Belfast to Thomas Nightingale Farmer.