On 20 January 1892, Abel executed an affidavit in furtherance of his pension claim for his service in the Civil War. He states "My true and only name is Abel Curnes. That it appears on my discharge as Carnes, but has been written Curnes for twenty or twenty-five years".
William Carnes, the father of Abel, apparently used "Carnes" his entire life, as did his children who stayed in Illinois where the family settled about 1845. Abel and his brother, John H. (who also served in the Civil War under the surname "Carnes"), both of whom resided for many years in central Iowa, consistently spelled their surname "Curnes" after they arrived in Iowa. Another brother, Reason F., settled in El Paso County, Colorado and spelled the name "Curns", as did his descendants. The name was spelled "Curnes" in the obituary of their sister, Elizabeth (married name "Campbell").
I am a descendant of John H. There is a story in the family that the spelling change was a result of an estrangement in the family (although we were told the name was originally spelled "Kerns"), but whether it was among the children of William or among William and his siblings, I do not know. It is also possible that the spelling change was a natural mutation based on pronunciation and later generations tried to explain it to their own satisfaction.