Murrumbidgee means 'track goes down here', 'a very good place' or 'big water'. (McCarthy; 1963). From Geographical Names Board of NSW: GEOGRAPHICAL NAMES REGISTER EXTRACT Available [online]http://www.gnb.nsw.gov.au/name/extract?id=ujjLjzxOIt

We are thus both right re the meaning but that big water meaning came from that arm waving thing so I dont take any notice of it.  The Aboriginal people were trying to warn my lot to not camp on the river flats because of the big water (arm waving here to try and get them to understand re floods) that happens and killed at least 89 out of 200 people in 1852.  'Track goes down there is the same as boss track.  Moorum means track.  beeja means boss.  Boss track.  Main track.  Main fault line.  (Rivers form within fault lines many times.  I live directly above it - the Ancrestral channel before he changed course - so know it.)