Let’s take a look at polite forms across languages.
How do we generally respond to someone saying “thankyou”? In English, the usual response is “you’re welcome”. But do expressions in other languages correspond to this, or do they actually mean something else? Let’s take a look at a few languages.
Slovenian: thankyou is hvala, and there are two main responses: prosim, which literally means “please” and ni za kaj, which means “it’s nothing”.
We see please as a response in other languages too: German bitte and Russian pozhaluysta (пожалуйста), in response to Danke and spasiba (спасибо) respectively. Not to mention Greek thankyou, efharisto (ευχαριστώ), being answered with parakalo (παρακαλώ); please.
“It’s nothing” is also popular. In Spanish, gracias can be answered with de nada, French merci gets a reply of de rien, while one possible response to the Italian grazie is non c’è di che. The other Italian word, prego, literally translates as “I pray”, as does the other French expression, je vous en prie.
Portuguese is a language with a great many ways to say thankyou. I won’t examine them all here, just briefly mention obrigado and agradecido. But here is the response: de nada or por nada, which of course corresponds to the Spanish de nada. But you can also say nāo há de quê, which means “there’s nothing (to thank) for”. Another interesting expression, perhaps best regarded as slang, in Portuguese is the use of valeu, which comes from the verb “to be worth” or “to be valid”, in informal situations to mean “you’re welcome”, and even “thankyou” as well.
And so we come to a language that uses the same expression as English. Welsh for “thankyou” is diolch, to which you answer croeso, which means “you’re welcome”, corresponding to both of the senses in English.
* And a big thankyou from me to @KnightGhost for her help with Slovenian and to @aefavant for the Portuguese.