Even if you don’t know Portuguese, you may have heard the word ‘Obrigado’, which means ‘Thank you’. And also, if you do not know Japanese, you may have heard the word ‘Arigato’, which means equally “thank you”.
An urban legend of Portugal says; ‘Arigato’ comes from ‘Obligado’. Portuguese brought this word when they came to Japan in 16 century and there was no such a word to express appreciations in Japan until that. This is why ‘arigato’ sounds similar with ‘obligado‘.
What I have to say is…it is not true! First of all, the sounds is not so similar (if you compare with other languages, maybe yes. But come on, it is not so similar). Also, it is wrong that there is no words of ‘thank you’ in Japan until the 16th century. We had it.
I explained every time this theory is wrong when Portuguese people tell me about it. They seems understanding my point but they somehow still believe in this theory.
For your information, ‘Thank you’ in Japanese comes from Buddhism. The original means is ‘it is difficult to be/exist’. In another word, it is so rare and how difficult to be born as a human.