"I wish somebody would tell me what "Doo wah diddy diddy dum diddy doo" means..."

It's a rather loose English translation of the original Gaelic "Well shirigim duraham da wack fall the daddy oh"

Actually as a result of changes in the English language over many generations it is what "Fa la la la la la la la la" became - and we *all* know what that means (nudge, nudge, wink, wink)