On the farm, sometimes, weeds will sprout out of cow patties. They are called "shitweeds". The term is also used for a person who is miserably disagreeable, an asshole
or a jerk
, but has a greater depth of meaning. It represents someone who is bad and worthless (like a weed) who was spawned by something equally worthless (like shit). A person who is a "shitweed" is similar to white trash
, a low and base person raised by low and base people.