"We're all Jock Tamson's bairns" suggests not only that we are all God's children and in the same boat, but that there are lots of Thomsons around. And indeed "son of Thom" has only recently dropped from 3rd to 4th place in the league of most common surnames in Scotland at the General Register Office in 1995. Thomson (without the 'p') is the most frequent spelling in Scotland; Thompson is found more in the North of England and Thomas in Wales.
The name is found most in central Scotland - there was a John Thomson in Ayrshire in 1318 who led part of Edward Bruce's invading army in Ireland on behalf of Robert the Bruce. There are Gaelic equivalents in MacTavish (son of Tammas) and McCombie (son of Tommy) and MacLehose is from the Gaelic 'mac gille Thoimis" or son of St Thomas.
Clan MacThomas was descended from Clan Chattan Mackintoshes and was based initially in Glenshee. The MacThomases supported King Charles I and the Marquis of Montrose but after the defeat of Montrose at the Battle of Philiphaugh, the chief withdrew his men and extended his influence into Glen Prosen and Strathardle. The chief approved of the stable government brought about by Oliver Cromwell and the Commonwealth. Consequently, after the Restoration of King Charles II the MacThomas fortunes declined and the clan drifted apart - some clansmen moving to the Lowlands and changing their name to Thomson or Thomas.
James Thomson (1700-1748) was a poet who wrote "The Seasons" which is regarded as a classic of English literature but is best remembered now for writing "Rule Britannia". Alexander "Greek" Thomson was a 19th century architect of note who is becoming more recognised at the end of the 20th. Robert William Thomson invented the pneumatic tyre in December 1845 and scientist and inventor William Thomson, though born in Belfast, became associated with Glasgow University and became Lord Kelvin. He gave his name to the measurement of temperature "Kelvin".
Clan McThomas, which is the only variant of the name recognised by the Standing Council of Scottish Chiefs, has a motto "Deo iuvante invidiam superabo" - I will overcome envy with God's help".
There is a Clan Thom(p)son site and there are Clan MacTavish/Thompson web sites here and here.
