the border, confine, or extreme, of a kingdom or province, which the enemies find in front when they would enter the same. Thus we say, a frontier town, frontier province, &c. Frontiers were anciently called marches.

The word is derived from the French frontiere, and that from the Latin frontiaria; as being a kind of front opposed to the enemy. Skinner derives frontier from front; inasmuch as the frontier is the exterior and most advanced part of a state, as the front is that of the face of a man.