(2 syl.). A border round a shield in heraldry. The origin of the tressure in the royal arms of Scotland is traced by heralds to the ninth century. They assert that Charlemagne granted it to King Achaius of Scotland in token of alliance, and as an assurance that “the lilies of France should be a defence to the lion of Scotland.” Chalmers insinuates that these two monarchs did not even know of each other's existence.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894