How did the word kangaroo become part of the English language?
The word "kangaroo" is believed to have come from the Aboriginal
word gangurru, a Guugu Yimidhirr word referring to the Grey
Kangaroo. Captain James Cook's botanist, Sir Joseph Banks, first
recorded the word as "kangaru" when the Endeavour was damaged on
the Great Barrier Reef near modern-day Cooktown, and required the
crew to stay on the mainland for almost 7 weeks repairing their
ship. This gave Banks ample time to make copious notes on the fauna
and flora, and to be certain of the Aboriginal word for kangaroo,
even though he had trouble translating it into written form.
It could be that "Kangaroo" is the name of a specific type of
kangaroo in one Australian aboriginal language. Europeans applied
the name to all similar creatures.
The story that the word kangaroo means "I don't know" is a
complete myth.