Since figurative language has always been a prominent source and feature of the cognitive approach to language study.
In Lakoff ’s experientialist approach (Lakoff 1987: 266) the human body and body parts (such as head/face, back/belly, leg/foot, arm/hand etc.) play an important role in our conceptualization of the world (e.g. to head in a direction, to look back, to let an opportunity slip through your fingers, to handle a problem, to know by heart , etc.).
The speakers of a language are constantly extending the existing resources of their language to new situations.
The wish for more expressivity is most of the time the cause for the creation of new metaphorical or metonymical extensions.
With time and a rise in frequency, these new forms can become conventionalized.