Blues guitarists

"Boo" means any sound at all

have I missed the observation that "diddley-squat" means nothing and Bo Diddley is a famous blues player so using 'Bo' could be an oblique substitution. if so, it would be a bit like cockney rhyming slang - replacing a word with another from a famous person e.g. a curry can be referred to as a 'ruby' - Ruby Murray=curry.