Hello, your assumption is a possiblity. If you go to this web address you will see a history of the three earliest O'Dair families I have located: http://familytreemaker.genealogy.com/users/o/d/a/Donald-K-Odair/FILE/0011page.htmlhttp://familytreemaker.genealogy.com/users/o/d/a/Donald-K-Odair/FILE/0011page.html The second Cornelius Neal O'Dair adair was married to an Elizebeth Davis. I have spoken with this person who has constructed this family history. He believes that the first Cornelius orginated from Edinburg Scotland. He has seen records that have indicated there was family in the Pennsylvania area. However, he has never researched this area as of yet. My family orginates from Pennsylvania from its records I can find. My web page is the following: http://familytreemaker.genealogy.com/users/o/d/a/Donald-K-Odair/?Welcome=1026397643http://familytreemaker.genealogy.com/users/o/d/a/Donald-K-Odair/?Welcome=1026397643 I have seen in many early Pennsylvania records where adair was used as O'Dair and O'Dair used as adair. The only way I sorted out my own family was to look at the acutal census. I then would determine the old english writing by looking at the A's and O'S of each census taker. My line of O'Dairs has a history of James being the dominate first name. My web site has many records I have found both in North America and International records as well.