Ed is correct , the Scot'sIrish tag is resented by us Scot's and Scot decent. Nothern Ireland are Scot's. In turn Chester Co,Pa is one of the Early American Scotland , family of Scotland and Ireland reunite here and Va. The variations of spellings come by error of the record recorder, and some did change the spelling for personal reason.
example: Robert Neely got on a boat as Robert Neely, but got off the boat as Robert Payne to excape assination , my surname Carruthers we hired a live in school teacher in 1740 and she change our spelling to the English variation Carothers , record keepers change , and omitted letters and some of the family still use these misspelling today.
Pollock's are Scot's , and truly not Irish , some of the family that carry the Sct'sIrish tag were only there long enough to change their sockes and catch a boat.