Boo

[Tony Glaser]

>  I'm not sure if this was mentioned in the discussion of "boo" (=nothing).
>I had often heard this word used in an expression to describe someone
>as overly timid: "He wouldn't say boo to a ghost." I suppose the
>original idea was that if you say "boo" to a ghost, the ghost would
>become frightened and disappear. Then by shortening; "He wouldn't say
>boo."
>   "Diddly-boo" is probably a blend of "diddly-squat" and "boo"
>rather than the starting point of "boo" (=nothing).
>
>---Gerald Cohen

In England the phrase I have heard more is "wouldn't say boo to a
goose". Or at least that's what my mother used to say.