تعریف و معنای "[talk] through the back of {one's} neck"

What is the origin of the idiom "talk through the back of one's neck" and when to use it?

The idiom "talk through the back of one's neck" does not have a clear or specific origin. However, it is believed to have emerged as a figurative expression to describe someone who speaks in a nonsensical, foolish, or exaggerated manner. The idiom is used to suggest that the person's words are coming from an illogical or nonsensical source, as if they were talking through the back of their neck instead of their mouth.