Thomson, Tomson, Thomison
Thomson, Tomson, Thomison—This name in Ulster and Scotland is a Scottish sept name principally of the Clan Campbell or Siol Diarmuid O'Duibhne. It is the anglicised form of a few names, especially M'Tavish and M'Cavish (Mac Thómhais) in North Antrim and the West of Scotland, and of M'Cause, M'Comish and McOmish; the latter three being McFarlane sept. In Gaelic Mac Thómais.
M'Cawis and M'Cause in 1491, in Killin of Lochtay, Scotland.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees