Sp means sponsor, the people who stand for the child, who promise to make sure the child is raised in faith correctly. This is usually a brother or sister of the parents or a close relative/family friend. These records are from notes I have on Carroll familys of louth (self complied). If you were to access the church records for Collon in Co Louth, you should get the same information. There is also and Irish Website that provides similar information for a fee.