"Macca":

A common nickname in some English speaking countries of Anglo-Saxon heritage (less commonly in Canada and the United States, where "Mac" is used) for somebody whose surname begins with the Gaelic prefix Mac or Mc (meaning "son of").

People frequently referred to as Macca include:

Sir Paul McCartney, English singer-songwriter, multi-instrumentalist, and composer
Chris McCormack (triathlete), Australian professional triathlete, two time ironman world champion
Amy Macdonald, Scottish singer-songwriter, guitarist, and recording artist
Andrew McLeod, former Australian rules footballer and two-time Norm Smith Medallist
Steve McManaman, former English footballer sometimes also called 'El Macca'
Stephen McPhail, Irish footballer
Gary McAllister, former Scottish footballer and manager
Gary McSheffrey, English footballer
Michael "Macca" MacKenzie, fictional recurring character on the Australian soap opera Home and Away
Steve McMahon, former English footballer
Bruce McAvaney, Australian Sports Media Broadcaster
Neil McKenzie, South African Cricketer
Paul McNamee, former Australian Tennis Player, now Sports Administrator
Steve McNamara, British rugby league coach and former player
Ian McNamara, Australian radio presenter, who hosts the ABC Local Radio program "Australia All Over"
Macca, guitar player of the rock band Be Quiet. Shout Loud!

Must admit if memory serves me correctly it only seemed to be commonly applied to Sir Paul McCartney post-Beatles.