' is a figure of speech
in which one thing is referenced by a something else which is only remotely associated with it. Often the association works through a different figure of speech, or through a chain of cause-and-effect. Oftentimes metalepsis
refers to the combination of several figures of speech into an altogether new one.
He's a lead foot.
We imagine a foot to be made of lead.
We know lead is heavy.
We imagine a heavy foot would press down on the accelerator all the time.
Hence, he drives fast.
We only get the meaning by a) metaphorically transferring heaviness from lead to feet b) seeing that a heavy foot causes fast driving.
See also: catachresis.