I was physically assaulted By a male coworker At work Who has also displayed other threatening behavior towards me He was not fired for assaulting me or the other threatening and inappropriate behavior he has aimed at me.
First, you have an assault claim against the co-worker. With respect to your employer, you need to take it to HR. If they do not act in some way that protects you, then you may have a claim against the employer.
It is not a "hostile work environment" in the legal sense that the term is used in discrimination and sexual or racial harassment cases. However, it is quite literally a hostile work environment! The kind of laws that you have available to protect you here is different than the laws intended to protect against harassment and discrimination in the workplace. This is good old-fashioned tort law. You can sue the co-worker for assaulting you, and if the employer fails to take steps to prevent this and it happens again, you may be able to sue the company for negligent hiring or negligent supervision.
The phrase "hostile working environment" is term of art used by lawyers. Putting that aside, you have assault claim against your coworker and should consider contacting the police. In addtion, you should consider approaching your company's HR department or your manager and reporting the incident as soon as possible. If the HR department or manager takes no action against the coworker for the assault, you likley have a claim against the company.