"One of the sailors pointed to the animals that hopped around with their young riding in pouches and asked an aborigine what they were called. The aborigine replied, 'Kanguru.' From then on Cook and his sailors referred to the animals by this word. It wasn't until later that they learned that it meant 'What did you say?'"
[Alas the story is almost certainly apocryphal.]
[Among the other words introduced by Cook from Polynesian languages: taboo and tattoo.]