The origin of the Expression, Fair Dinkum
The first true bush people of Australia's outback, were the race of small people called THE DINKUMS. They taught the Aboroigines all they knew about reading tracks and how to find their way around the deserts.
The friendly FAIR HAIRED DINKUS gave the early settlers travelling across Australia, precise directions on how to reach their destinatios safely.
Unfortunately ... there were walways a few DARK HAIRED DINKUMS who were born liars and would intentionally disdirect the unwary traveller. (It's thought that the famous Australian explorers, BURKE and WILLS received their last directions from a DARK HAIRED DINKUM!) aND WE KNOW WHAT HAPPENED TO THEM!
So...to this very day...if an Australian human tells you womething that you know is true - you can be assured it is well and truly FAIR DINKUM!