People say fiddlesticks when they disagree, or when they are a little annoyed — a mild “that’s nonsense” or “oh, come on”. It is old-fashioned and a little playful. You can hear it from older British speakers, or in children’s books that want a strong feeling without a strong swear-word. Younger people almost never say it unless they are joking, copying a grandparent, or acting in a play. You will also see Fiddlesticks! as a one-word reply. It is not rude. It is not strong. It is closer to “rubbish!” than to real anger. Though actually, the word first named a violin bow (a fiddlestick). How a bow became a huff of disagreement is not something the pieces themselves explain; people in England just started using it that way around 1600. When someone says it, they are not talking about music.

「少來了！」「胡說！」（溫和、偏老派、帶英式幽默的語氣詞；不是在說琴弓）