Max Müller is mentioned as one of the pioneers of the study of the origins of language, as he created a typology for the earlier origin of language theories based on the channel they draw the connection between sounds and meanings upon.
The ding-dong theories were supposed to see the connection in some kind of "natural resonance". I don't think Müller refers to actual sound resonance. In his work, he doesn't mention much more than Wikipedia: "Müller suggested what he called the ding-dong theory, which states that all things have a vibrating natural resonance, echoed somehow by man in his earliest words." This "natural resonance"
Did he meant something along the lines of: "There IS some kind of mysterious connection but we don't know what's behind it."? Or does the "natural resonance" actually refer to the "concept of the word" - (for ex. "kiki" is made of short and intermittent sounds)?
EDIT: No longer valid source switched for Wikipedia.