Is Polyamory Just a Renamed Swinger Lifestyle or Open Marriage?

No. This is a common misconception.

Swinging, open marriage, and polyamory are all forms of ethical, disclosed, or consensual nonmonogamy, meaning none of them are cheating, but they aren’t the same thing as each other.

Swingers have casual sex at clubs, events, or parties, usually ones that are mainly there or being held for the swinging element. Couples (and triads, and...) who swing have agreed with each other to do so.

Polyamory involves having a dating, romantic, partner, or spousal relationship with more than one person in a way to which those involved have agreed. For example, three people might live together as partners with each other in a triad. Or, one person might have ongoing dating relationships with three different people, none of whom spend time with each other, but all three of them are aware and agreeable to the fact that the person they are dating is seeing other people, not for the purposes of “picking” one of them, but on a continuing basis. Each of them may or may not be seeing or living with other partners. Polyamory can take many different forms.

An open marriage or open relationship is a marriage or relationship that isn't closed to new partners. The people in the marriage or relationship have agreed that one, both, or all of them are open to finding new partners, whether separately or together, whether those partners are for casual sex (like with swinging, or hookups, or threesomes) or a spousal relationship (like with polyamory), or some other way.

People in an open marriage or open relationship might swing, or might be polyamorous, or might look for casual encounters that aren't part of swinging. But many polyamorous people are in closed relationships and aren't open to having new partners. Some swingers consider their marriage or relationship only open for swinging and not anything else; it's not a generally open relationship and neither or none of them are looking for anyone outside of the context of swinging.

So...

Swingers may or may not consider themselves polyamorous.
Polyamorous partners may or may not swing.
Swingers might be in an generally open relationship or only be "open" for swinging.
Polyamorous relationships can be open or closed.

Whether you know it or not, you know people who are in consensually nonmonogamous relationships. You know people who are, or have been, swingers. You know polyamorous people. You know people in open relationships. People of all walks of life find these forms of ethical nonmonogamy suit them and their relationships. Some of them are health care providers, firefighters, accountants, airline pilots, military personnel, engineers. lawyers, educators, clergy, or stay-at-home parents.

Nonmonogamous people shouldn't be discriminated against or denied their rights. Let people have the relationships to which they've mutually agreed.