The Piercèd Heart is taken from the arms of the Logan family (one of the component families of Clan MacLennan) and alludes to a posthumous service performed for Robert the Bruce, King of Scots, who died 7 June 1329. Quoting now from The History of the MacLennans, by Ronald George MacLennan of MacLennan, 34th Chief of Clan MacLennan (Inverness: John G. Eccles Printers Ltd., 1978), pages 151 and 152 {quoted by the gracious permission of the late author}:
... because [King Robert the Bruce] made his solemn vote to pass with an army in defence of the Christian faith against the Turks, and as prevented by untimely death, he left his heart to Christ and chose his true knight Sir James Douglas to pass with it to the holy `grail'." ... In compliance with the King's instructions Sir James Douglas chose seven of the most distinguished knights in the kingdom among them being Sir Robert Logan, Sir Walter Logan and Sir Walter St. Clair (Sinclair) younger of Roslin as his companions ... [Douglas] heard that Alonzo, King of Leon and Castile was waging war against Osman, the Saracen King of Granada, and as he was on a religious mission against the infidels, he determined to land in Spain. King Alonzo received them hospitably and invited the Scottish knights to help him in the war.
On 25th August, 1330 at the battle of Theba, the Saracens were defeated. Sir James Douglas, who was a most distinguished soldier, and experienced in warfare, had little difficulty in putting to flight the Saracens opposed to his troops, but not knowing their tactics some of the party pursued the enemy too far. The Moors when they saw the Scots scattered from each other in the chase, suddenly turned back, and surrounded Sir William St. Clair. Douglas, with Sir Robert and Sir Walter Logan galloped to the rescue but finding the enemy pressing round in increasing numbers and with no chance to escape, Douglas took Bruce's heart from his neck, round which encased in a silver casket and chain he wore it, and threw it forward amongst the enemy saying, "Pass first in fight as thou wert wont, Douglas will follow thee or die." He then dashed forward, cutting his way through the enemy, but the odds were too great, and he and the two Logan knights, Sir William St. Clair, and his brother John were all slain. Douglas's body was found lying over Bruce's heart, and his followers brought it, and the casket back to Scotland to which they sorrowfully returned. The King's heart was buried in Melrose Abbey.
For their part in this exploit, the family of Douglas were granted a crowned heart, while the Logans were granted arms consisting of a heart pierced by a passion-nail (or, in some cases, three "piles" or slivers) and the motto Hoc Majorum Virtus, which, being translated, is This is the valour of my ancestors.