What's the meaning of the word 'Fiddlesticks'?
An exclamation made to indicate "nonsense; rubbish".
What's the origin of the word 'Fiddlesticks'?
The term fiddlesticks derives from the literal 'fiddle sticks', that is, the bows that are used to play violins. Those have been named in English since the 15th century - then as 'fydylstyks'.
The word was appropriated to indicate absurdity in the 17th century. Thomas Nashe used it that way in the play Summer's Last Will and Testament, 1600:
A fiddlesticke! ne're tell me I am full of words.
There's nothing inherently comic about a violin bow. It seems that 'fiddlestick' was chosen just because it sounds like a comedy word, like 'scuttlebutt' (a cask of drinking water), 'lickspittle' (a sycophant) and 'snollygoster' (an unprincipled person).
In the same way the 'I don't give a fig' was originally 'I don't give a fig's end', that is, it referred to something insignificant, 'fiddlesticks' was originally 'fiddlestick's end', that is, it was a reference to something paltry, trifling and absurd.