I've just returned from a short break in Lisbon. I don't know Portuguese, but I do like to learn a few useful and polite phrases when travelling to a country, so I know that obrigado means 'thank you'. I found I kept getting confused with arigato, which is 'thank you' in Japanese.
Portuguese explorers were the first Europeans to visit Japan in the 16th century, and a number of words in Japanese have a Portuguese origin, but not, it turns out, arigato, which was in use in Japan before the Portuguese came. The similarity in the words must be coincidental.
Words in Japanese that do come from Portuguese include pan, bread (from pão), botan, button (botão in Portuguese) and the name of the Japanese dish tempura, which, according to the OED, is probably from the Portuguese tempêro, seasoning. These words are now written in kanji ie as characters, which shows that they are fully assimilated into Japanese these days. For other Portuguese loan words in Japanese see this Wikipedia page.
Words in English with their origins in the Portuguese language include cobra, emu, marmalade, molasses and many more.