How does the std trichomoniasis originate?? i understand it is a parasite and is passed from penis to vagina, vagina to vagina, etc, but how does it begin? from an unclean penis/vagina that wasn't washed properly?? what invites/feeds the parasite??

Trichomoniasis doesn't "begin" or "originate" anywhere. Every case is caught from someone who already has it; the trich parasite evolved in humans and probably for thousands of years has been transmitted from person to person, primarily by vaginal intercourse. Hygiene or cleanliness has nothing to do with it. It feeds on chemical nutrients that occur naturally in the vagina and urinary tract.

It occurs like any parasite e.g. bacteria, fungi or microscopic organism causing disease by invading the body by many routes depending on the organism. It then thrives on the area invaded. Trich.- on the vaginal/ penile inner lining and can be passed on by various kinds of sexual activity- clean or otherwise.