Townlands of Brierfield, Abbeyknockmoy, Galway

Hello!  I am researching my Grady and Burke ancestors from East County Galway.  In scouring Griffith's Valuation, I have found who I believe is my paternal 2nd Great Grandfather, Martin Grady, in Brierfield South, Abbeyknockmoy, Galway!  But I see there a Brierfield North, Brierfield Burke, Bierfield Blake,Brierfield Stevens (or Stephans) and Brierfield Toole!  I wonder if anyone can tell me how these Townlands came to be named in this manner as I don't believe I've ever seen other townlands distinguished from each other by surnames!  And if that is the purposed (i.e. to distinguish the areas), how might the surnames have been chosen?  Thanks for any light you may be able to shed on this subject!    Pat Peoples