Trampling have a sexual connotation, especially
when in relation to BDSM. It involves the act of the dominant
(usually a woman) stepping on and walking all over the submissive.
This can be done sensually and barefoot, or more to cause pain with
high heels or other shoes.
The psychology behind it is that the submissive is "underfoot" the
dominant, and is below her (literally and figuratively).