Papillon Bleu - whose blog I love to visit - asked me recently whether I'd heard the story that the Australian word kangaroo means I don't know in an Aboriginal language.
I've heard the story, but it didn't seem likely to be true, so I had a look in a couple of reference books on my shelf. They're general interest books, not specialist books, but they did have some information about this word.
Aboriginal Words of Australia, originally published way back in 1965, didn't have much. It does mention that the Aboriginal people at the time of early settlement by Europeans thought this was an English word, and also refers to the story that it meant 'I don't know', but says there is no evidence for this theory.
Australian Aboriginal words in English, Their Origin and Meaning, first published in 1990, points out how unlikely it was that any Aboriginal person would have said they didn't know the name for a kangaroo, given that it was a staple food throughout the continent.
The reference says this is the first and best-known borrowing of an Aboriginal word into English. Cook learned it from local people in 1770 when he was forced to make repairs to the 'Endeavour' in north Queensland. It was the local language's term for one particular species of dark grey kangaroo but the Englishmen thought it was a general term for a variety of marsupials and the speakers of other Aboriginal languages supposed the unknown word was an English term.
The really funny part is that the local Aboriginal people in one place thought it was the English word for 'edible animals' and it eventually was taken back into one language as the local word for a horse.