The surname of Sinclair in French is “de Sancto Claro” and in Latin, “Sanctus Clarus,” meaning Holy Light.

In return for his efforts, the king supposedly granted Sinclair the barony of Roslin, Scotland "in free heritage".

[12] The chiefs of Clan Sinclair, the Earls of Caithness, descend from William St. Clair who was sheriff of Edinburgh and who was granted the barony of Roslin (Rosslyn) in 1280.

[13] During the Wars of Scottish Independence, Sir William Sinclair of Rosslyn was captured at the Battle of Dunbar (1296) and died later, probably in the Tower of London.

[11] In 1303 the Battle of Roslin took place where Scots under Henry Sinclair of Rosslyn and the Clan Comyn defeated an English force.

[13] The Battle of Loudoun Hill took place in 1307 where Scots under Robert the Bruce, assisted by Henry Sinclair of Rosslyn again defeated the English.

[13] The family initially favoured John Balliol's claim to the throne but later it became paramount that they gave their loyalty to Robert the Bruce.

[13] The Battle of Donibristle took place in 1317, William Sinclair, Bishop of Dunkeld, rallied the Scots army to defeat an English invading force in Fife.

[13] Henry I Sinclair, Earl of Orkney, Baron of Roslin, and Lord of Shetland (c.1345-c.1400), was a Scottish explorer nobleman.

He is also alleged to have voyaged as far as the Americas in 1398 (being hypothetically identified with Zichmni, who travelled with the Zeno brothers, for the first time by Johann Reinhold Forster in 1784[14]); believers in this hypothesis claim he possibly landed in both Massachusetts and Nova Scotia.

[12][18] William Sinclair, 2nd Earl of Caithness was killed fighting for James IV of Scotland at the Battle of Flodden in 1513.

[22] On 3 April 1593, George, 5th Earl of Caithness resigned his earldom in return for novodamus and remainder to his son William Sinclair.

[13] In 1657, George Sinclair 6th Earl of Caithness was present when Oliver Cromwell was proclaimed Chief Magistrate of the three nations in Edinburgh.

[13] In 1680 a feud took place between George Sinclair of Keiss and Sir John Campbell of Glenorchy over the right to the lands and title of the earldom of Caithness.

This resulted in the Battle of Altimarlach, where, legend has it that so many Sinclairs were killed that the Campbells were able to cross the river without getting their feet wet.

[13] In 1736, Sir James Sinclair of Rosslyn resigned his office as hereditary Grand Master Mason of Scotland to the Scottish Lodges on their foundation.

[11] On 17 June 1739 Major Malcolm Sinclair 'A good and faithful servant of Sweden' was charged with affairs of State, he was assassinated at Grunberg in Silesia by agents of Tsaritsa Anna of Russia.

[13]\ On 4 June 1745, Sir James Sinclair of Rosslyn, a lieutenant general with the Royal Scots regiment, was appointed the commander of the British Forces in Flanders.

[13] At the Battle of Culloden in 1746, Sir James Sinclair of Rosslyn commanded the Royal Scots regiment on the British-Hanoverian government side.