Marches (boundaries)
is the Saxon mearc; but marsh, a meadow, is the Saxon mersc, anciently written marash, the French marais, and our morass. The other march is the origin of our marquis, the lord of the march. The boundaries between England and Wales, and between England and Scotland, were called “marches.”
Riding the marches—i.e. beating the bounds of the parish (Scotch).