I have been doing a little research on The MacThomas Clan. It's a sad (but not uncommon) story of a clan so rooted in their lands that they ignored what was going on in distant places such as Edinburgh. They were successful cattlemen at the start of the 17th century but they had their enemies, and in 1676 the MacThomas lands in Glenshee were sold as a result of law suits and fines for not paying fines.
a history of the clan which was launched at The Gathering in Edinburgh last year.
And if you wonder where 'Finegand' comes from, it is a corruption of the Gaelic feith nan ceann, meaning burn of the heads. It seems that the Earl of Atholl sent some particularly officious tax gatherers across to Glenshee and the MacThomases took exception to this. They used their dirks and tossed the taxmen's heads into a nearby burn. Perhaps that is what is being conveyed by the clan crest.
Would that it were that easy to deal with officious officialdom nowadays!