Q: When someone says “thank you” in Spanish or French, the usual reply is “it’s nothing.” Why do we say “you’re welcome” in English?
A: Let’s begin with some history. The word “welcome” is a very old word, dating back to Anglo-Saxon days. The first published references in the Oxford English Dictionary are from Beowulf.
The word was originally wilcuma in Old English, a combination of wil (pleasure) plus cuma (guest). At first, it could be a noun for a desirable guest, an adjective describing such a guest, or an interjection greeting the guest. The verb form, wilcumian, meant to receive someone with pleasure.
By about 1300, however, “welcome” was being used more loosely to describe something acceptable, pleasurable, freely permitted, or cordially invited.
So when did we begin using the word in response to “thank you”? The language sleuth Barry Popik has traced the usage back at least to Shakespeare’s day. Here’s an exchange from Othello (circa 1603):
Lodovico: Madam, good night; I humbly thank your ladyship.
Desdemona: Your honour is most welcome.
I don’t know when the exact phrase “you’re welcome” was first used in response to “thank you,” but I can attest from personal experience (and a few reminders from Mom) that it was before the OED’s first citation.
The earliest reference in the OED is from a 1960 newspaper article, though the dictionary has one from a 1907 short story that’s quite close: “Thank you,” said the girl, with a pleasant smile. “You’re quite welcome,” said the skipper.
[Update, Oct. 4, 2016: A reader found an earlier citation in The House by the Churchyard, an 1863 novel by the Irish writer Sheridan Le Fanu: “ ‘I thank ye again, sir.’ ‘You’re welcome, my honey,’ rejoined Toole, affectionately.”]
Why “you’re welcome”? I can’t give you a definitive answer. But I suspect that it’s simply another way of saying “it’s a pleasure” or “the pleasure is mine.” Remember, one of the early uses of “welcome” was to describe something pleasurable.
As for the Spanish de nada and the French de rien, we too sometimes say “it’s nothing” in response to “thank you.” Also, Spanish and French speakers sometimes say “the pleasure is mine” (el gusto es mío and le plaisir est pour moi).