One good source for the Carr/Kerr line is Burke's Peerage. Using that, Geni, Ancestry, the Carr family books, etc. I have traced Nancy Elizabeth Carr back to 1085, although many sources differ on where the original Kerr's came from Kind of have to decide which source you want to believe
One theory is our remote forebears left Southern Norway with RoIf the Ganger — or Rollo the Walker — thus called because he was too tall and long-legged to ride, and therefore strode ahead of his berserkers on their ponies. They settled in the angle of Brittany and the Cherbourg peninsula in 911, then came to England in 1066 in the retinue of de Bruys, the ancestor of the Bruces. He took up land near Preston and they received their small share of it as his gamekeepers, an occupation also followed by John Ker of Stobo four generations later (the "Hunter of Swynhope" and the first recorded Scotsman to bear our name; he is mentioned as taking part in a rough-and-ready land survey, or "perambulation", in 1190).
The alternate theory is that the line of the Carr family goes back to the Old Testament times to a tribe which were standard bearers to the King. The name in Hebrew was Kir (Isaiah 15:1 and 22:6). The word Ker (Kir) signifies strength and carried this same meaning in the Bible.
Many of the Kers, Keers, Kerrs, earrs, Carres, Carrs in the British Isles, Scotland and Ireland have been traced to one Baron William Karrie (Karre), who came from France with William, Duke of Normandy and fought at Hastings in 1066. His name appears on the Role of Battle Abbey as "Karre", which was suspended in the Abbey. His posterity evidently settled in the north of England and during succeeding generations migrated into Scotland and Ireland. His descendants, two brothers, Ralph and John, passed over into Scotland from England during the 13th century and founded the two illustrious Houses, Carr of Fernhihurst, now represented by the Marquess of Lothian and Kerr of Cessford, whose chief is the Duke of Roxburghe.