So hear me out.
Cats go, “[i]Meow[/i],” right?
Then guitars go, “[i]Neow[/i],” if you make the sound effect with your mouth.
They make the same sound, except the first letter of the word is different.
Conclusion: Guitars are instrument cats
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I've never once heard Beavis and Butthead ever go 'neow' when doing guitar sounds. Your theory is bust.