PHRASES AND IDIOMS
TO BE UP A GUM TREE:
With most phrases it is the origin rather than the meaning that is in doubt. 'Up a gum tree' has several meanings. The most commonly used is 'in great difficulties'. Other meanings are 'in a state of contentment' or 'with great speed'.
What's the origin of the phrase 'Up a gum tree'?
up a gum tree, The phrase originated as 'like a possum up a gum tree' and interpretations of this account for the variety of meaning. The allusion is to possums escaping up trees after being chased by hounds. Depending on one's point of view the possum could be said to be either in difficulty as it couldn't escape, relaxing contentedly because the hounds couldn't catch it - either way it would probably have shown a good turn of speed up the tree in the first place.
Gum tree is the common name for the Eucalyptus in Australia and the Black Gum or Tupelo in North America.
The saying 'up a gum tree' is generally thought to be Australian. Noted etymologists like Eric Partridge list it as such. That may be so, it certainly sounds Australian, but the earliest citation of it in print I can find is from the USA, in a 1829 edition of American Speech:
"Dere's possum up de gum tree."
-Ramesh Chandra Khankeriyal