For the benefit of anyone else researching this line of Kaighins/Carns, I am pasting from an email I sent to Steve:

Hugh Kaighin was christened 4 Sep 1791 at Kirk Michael, Isle of Man. He was the second son of Hugh Kaighin and Catherine Killey of Kirk Michael. Hugh married Eleanor Cannon 20 Dec 1823 at Kirk German, Isle of Man. That marriage produced eight children. The first two, Catherine (c. 28 Nov 1824, K. German) and Anne (c. 21 May 1826 K. German) were born in the Isle of Man. The remaining, Joseph, Eleanor, Susannah, James, William and Charles were all born in Ohio.

Hugh and Eleanor emigrated in 1827 aboard the Barque Ocean with their second daughter Anne. For a reason still undiscovered, they left their eldest daughter Catherine behind to reside with her Cannon grandparents. She later married attorney Joseph Woods and is mentioned in her grandmother Elinor Cannon's will in 1857. The family was bound for the Manx settlement in Painesville, Geauga County, Ohio. Hugh soon bought land and farmed it in LeRoy Township (which is now in Lake County, Ohio).

Regarding the name change. I have never come across an 'official' reason for changing his name, but I don't think that he ever legally changed it to Carn. My own guess is that the pronunciation was difficult for the natives here in America. In the Isle of Man, the name was, and still is pronounced "Kack'n". He probably wanted to soften it a bit so he took the nickname 'Carn' and it eventually stuck. Interestingly, while researching for this email, I discovered his 1840 US Census record where he is shown as "Carhun", and in 1870, he was enumerated as 'Carghin', so maybe the name just sort of evolved. Another theory I have, is that he combined Kaighin and Cannon to come up with a hybrid 'Carn'. Whatever the case, as late as the 1860 census he was enumerated as Kaighin. Hugh died June 7, 1877 and is buried with his wife and several children in Brakeman Cemetery, LeRoy Township. The names Carn and Kaighin were both used on the headstones.

The children of Hugh Kaighin/Carn and Eleanor Cannon were as follows:

Catherine, c. 1824 11 28 - Kirk German, Isle of Man, bur. 25 Jul 1917, Kirk Braddan, IOM, married Joseph Woods
Anne, c. 1826 05 21 - Kirk German, Isle of Man, died 2 Oct 1890, unmarried, deaf and dumb
Joseph b. abt 1828, Leroy Twp, died 25 Dec 1850, unmarried, deaf and dumb
Eleanor b. abt 1830, Leroy Twp, died 9 Jun 1866, unmarried, deaf and dumb
Susannah b. abt 1834, Leroy Twp, died 8 May 1918, married John Orlando Hopkins, resided in Buffalo, NY; Rockton, IL and Janesville, Wisconsin
James b. abt 1836, Leroy Twp - I don't know what happened to James - he was not buried with his family
William b. abt 1840, Leroy Twp, died 12 Jun 1858, unmarried
Charles b. July 1842, Leroy Twp, OH, died 10 Jan 1921 - more below.

Son Charles Carn married Lydia R. UNKNOWN about 1873. That marriage produced one daughter, Margaret who was born in April of 1891. Margaret cannot be found after the 1900 census. Charles remained at the farm in LeRoy. By the 1880 census, he had taken over the farm and his mother Eleanor was still alive. He is also in the 1900 ,1910, and 1920 censuses. He retained the name Carn until his death in 1921. His death is recorded in the State of Ohio Death Index
Ohio Death Certificate Index 1913-1937:
Charles Carn, Cert. # 3662. 10 Jan 1921, Lake County.
Lydia A. Carn Cert # 10217. 27 Feb 1927, Lake County.