Walker
Walker—This name in Scotland and North-East Ulster is the anglicised form of Nucator, and other forms are found in different parts of Scotland as McNucator; M'Knockitir in Morayshire; correctly in Gaelic written Mac An Fhucadair, the name meaning the “Son of the Cloth-fuller.” The name was connected with various Scottish septs, but I haven't found one of Irish origin, except Mac Súibhlaigh.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees