"A mari usque ad mare" (French: "D'un océan à l'autre", English: "From sea to sea") is the Canadian national motto. The phrase comes from the Latin Vulgate translation of Psalm 72:8 in the Bible:

"Et dominabitur a mari usque ad mare, et a flumine usque ad terminos terrae"

(King James Bible: "He shall have dominion also from sea to sea, and from the river unto the ends of the earth").

The motto was first officially used in 1906 on the head of the mace of the new Legislative Assembly of Saskatchewan. This phrase was suggested for a national motto by Joseph Pope, then-Under Secretary of State, when the Canadian coat of arms was redesigned in 1921. Pope was a member of the four-person committee appointed by the federal government to redesign the coat of arms (the other members were Thomas Mulvey, A.G. Doughty and Major-General W.G. Gwatkin). No motto had been included in the original design. Major-General W.G. Gwatkin proposed "In memoriam in spem" ("In memory, in hope") as a motto, but Pope's proposal garnered more support. The draft design was approved by Order in Council on April 21, 1921, and by the Royal Proclamation of King George V on November 21, 1921.

More Info: en.wikipedia.org