My surname is Carroll (only one generation ago it was O’Carroll) and this is what the website told me:
O’Carroll is the anglicized form of the Irish name "O'Cearbhaill" which was a byname for either a butcher or a fierce warrior, deriving from "cearbh", which means hacking or to hack. There were six distinct sects of O'Carroll in Ireland, namely in County Kerry (where my parents are from), and County Tipperary.
The hacker/butcher/ fierce warrior bit I do like the sound of and combined with my first name (Louise) which also means warrior, I sound like someone not to be messed with.
I like that!