http://personalpages.manchester.ac.uk/staff/andrewkg/ass.final.pdf
We refer to these expressions collectively as “your ass”. Your ass is not simply a possessive
pronoun + NP (PossNP) construction since, primarily, it is semantically non-compositional,
This is clearly evidenced by (1c), where it is the members of the band who know how to
jam (not their buttocks) and likewise the speaker presumably handed the ten dollars to the
woman with his hands (not his buttocks).
