My surname is Buchan, the district I live in (in Scotland) is named Buchan, it’s a name common only to this area and the clan Buchan chief has his estate here. If you were to dig straight down until you come out the other end, in Victoria between Sydney and Melbourne there’s a place called Buchan. There’s a Buchan river and amazing Buchan caves https://www.parks.vic.gov.au/places-to-see/parks/buchan-caves-reserve

They think the name Buchan has aboriginal roots, but it was probably named by either an extradited riffraff Buchan criminal or perhaps a not so skilful Buchan fisherman who got lost and just kept going.