The Welsh Marches (Welsh: Y Mers) is an imprecisely defined area along the border between England and Wales in the United Kingdom. The precise meaning of the term has varied at different periods.
The English term Welsh March (in medieval Latin Marchia Walliae) was originally used in the Middle Ages to denote the 'marches' between England and the Principality of Wales in which Marcher Lords had specific rights, exercised to some extent independently of the King of England. In modern usage, "the Marches" is often used to describe those English counties which lie along the border with Wales, particularly Shropshire and Herefordshire, and sometimes adjoining areas of Wales. However, at one time the Marches included all of the historic counties of Cheshire, Shropshire, Herefordshire, Worcestershire and Gloucestershire.
In this context the word march means a border region or frontier, and is cognate with the verb "to march," both ultimately derived from Proto-Indo-European *mereg-, "edge" or "boundary". (Wikipedia)