What are the prefixes for all counties?

Carlow (CW), Cavan (CN), Clare (CE), Cork (CK), Donegal (DL), Dublin (DN), Galway (GY), Kerry (KY), Kildare (KE), Kilkenny (KK), Laois (LS), Leitrim (LM), Limerick (LK), Longford (LD), Louth (LH), Mayo (MY), Meath (MH), Monaghan (MN), Offaly (OY), Roscommon (RN), Sligo (SL), Tipperary (TY), Waterford (WD), Westmeath (WH), Wexford (WX), Wicklow (WW).