Complex sentence: The plain takes its name from Cumberland, one of the 39 traditional counties of England--a name it shares with Cumberland County, the cadastral division covering much of present-day Sydney and the Cumberland Highway.
Split into simpler sentences: The plain takes its name from Cumberland, one of the 39 traditional counties of England. The Cumberland County is one of the the cadastral land divisions of New South Wales, covering much of present-day Sydney and the Cumberland Highway.