Quinoa

the 3rd Edition of the Oxford Dictionary (2010) does list it and says it is from the Spanish, so Qu must be pronounced k in Spanish etc. It doesn't say what the original South American spelling was, if they had one.

The original "spelling" was probably a bunch of Incan hieroglyphs, but the usual spelling in the modern language is "kinua".

The Spanish borrowed the word in the 17th century, but they spell the "k" sound as "qu". Hence the language's name, Quechua (pronounced "ketch-wa"), is usually spelt the Spanish way, even though ordinary words are usually spelt with a k. E.g. the Quechuan word for "two" is "iskay".

Yes, I am a linguistics nerd! (Though I got some of the above from Wikipedia.)