Ancestry website gives 'rath' as a Germanic name implying 'advice' or 'counsel' as well as land clearing.
'Rath Name Meaning
German and Jewish (Ashkenazic): descriptive epithet for a wise person or counselor, from Middle High German rat ‘counsel’, ‘advice’, German Rat ‘counsel’, ‘advice’, also ‘stock’, ‘supply’.German (also Swiss Räth): from a short form of any of the various Germanic compound personal names formed with rad, rat ‘counsel’, ‘advice’ as the first element.German (Rhineland): habitational name from any of various places called Rath, which derives from Middle Low German roden, raden ‘to clear land for cultivation’.Irish: in some cases a habitational name from a place called Rath; in County Derry it is a reduced form of McIlwraith (see McIlrath).'
We still get Rathaus in German for town hall.
On the other hand Wiktionary gives us the Irish meaning
'(historical) A walled enclosure, especially in Ireland; a ringfort built sometime between the Iron Age and the Viking Age'
Which may well be from the same source. The fairies were famous for their raths.
'Fairy forts (also known as raths from the Irish, referring to an earthen mound) are the remains of lios (ringforts), hillforts or other circular dwellings in Ireland. From (possibly) late Iron Age to early Christian times, the island's occupants built circular structures with earth banks or ditches. These were sometimes topped with wooden palisades, and wooden framed buildings. As the dwellings were not durable, in many cases only vague circular marks remain in the landscape. Raths and lios are found in all parts of Ireland'
Given the similarity in meaning between the gaelic and nordic worlds it could well point to areas where the two cultures came together as part of the trading empire.