i don't think pussy comes from the term for a vagina
i always interpreted it as calling someone a cat, since cats are easily scared by everything
alternatively, it could come from the word "pusillanimous".
and i'm not even sure why trash and parasite are there
While the terms have different origin, langage evolved and cimented their usaged within the frameworks of domination. For "pussy" the usage to describe female genetalia quickly turned into a "emasculating" injonction : "don't be such a pussy". Which is directly link to patriarchy.
For parasite and trash, these terms, while describing different things, are now usually used as a weapon of language against lower classes of economic background.
Trash, is the least "significant" if I might say, but it still revers a form of class disdain that parasite hold very strongly. You will find "parasite" mostly in dehumanizing terms and most of the time directed toward marginalized people under capitalism.
"Parasite", "Pussy", "cunt", "retard", "*****", "skizo" and so many more... are insults directly linked to domination system. The "extasy" toxic people might feel when using these words is created through the position in the hierarchy of each ones of these dominations and the exctasy of trying to shuv a person down the ladder.
Usually, these will be used against people who they are directly targetting (
women, black people, psychiatrized people, poor people) which is why they must be stopped. Not because they are bad words in themselves, but because they are part of a panel of weapon used to attack people who are already facing domination in one way or another.
One insult is is just one insult... but a flow of a coherent dehumanization is a real problem.
The control of language alone will not stop racism or classism or sexism, but it will at least help in creating places where people who are directly targeted will be able to express themselves without the fear of these harmfull insults. If toxic individuals were moderated when they are throwing me sanist and classist insults.. perhaps more people would think about sharing about their experiences.