Coolson, Coulson
Coolson, Coulson—These two names are later anglicisations of McCoul and McCool, found in the Isles, Argyleshire, Donegal and Derry, in Gaelic Mac Cumhaill.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees