Fascinating etymological discussion but returning to the new coach service it's something of a Cook's Tour of South Wales and the West Country.
It will operate between Swansea and Bristol Airport as a limited stop service, calling at Cardiff Bus Station, Newport Railway Station, University of the West of England (Frenchay Campus) in North Bristol and Bristol Country Bus & Coach Station.
Anyone living in or visiting Cardiff, Swansea or Newport who want to use Bristol Airport can already do so via the Bristol Airport Flyer and the rail connection at Bristol Temple Meads Railway Station with through ticketing. The 10-minute Flyer frequency for much of each day with reduced frequency late evening and through the night together with the 30-minute rail frequency between Bristol and Cardiff seems a much better bet than touring Severnside by coach.
The Flyer carries over 600,000 passengers a year between airport and city centre stops with the majority of them rail passengers via Temple Meads, including a substantial number originating or terminating in South Wales.
If the Greyhound venture is to succeeed at all it will be more likely to do so by conveying the general public between the cities of Cardiff and Bristol where there is no direct (sorry!) bus service - a change of bus is required at Newport - and possibly by picking up a few for the airport in North Bristol.
I think this 'further nail in CWL's coffin' is more in the perception than the reality because an acceptable means of public transport already exists for those who want to transit BRS from/to the Welsh cities that the coach will serve.