The origin of 'fair dinkum'

"The debate is still going on about the origin of the expression 'fair dinkum'. One opinion is that 'dinkum' is a Cantonese word meaning 'true gold'. Apparently, the Chinese would call out 'dinkum' when they struck gold. Another opinion is that it is really an English word originating at Lincolnshire and meant 'a day's allocation of work'. Whatever its origin, today 'fair dinkum' is well and truly part of Aussie slang and means something or someone to be genuine or true."

- John Morris in The Fair Dinkum Queensland Exposed!