scud : sour
The Illunse word for sour is scud. Scud is a ballistic missile developed by the Soviet Union. In English scud means to race along swiftly (especially used of clouds). Scud: The Disposable Assassin is a science fiction comic and video game.
This word is a mixture of the Old English word súr (sour, tart, acid; made sour, fermented), and the Latin word acidus (acid / sour / bitter / tart; sour-smelling; soaked in vinegar).
I don't tend to use words that mean something in English, but I'll do it here.
I couldn't find words for sour in either Quenya or Sindarin.