Yes :) In older times when the French was more popular and Poles pronounced image as "imaż", not "imydż" waiters (and some assistants in hotels) were also called garson.
- Odźwierny (jaintor? doorkeeper?) is a person that is hired to stay near the entrance to greet guests was called szwajcar (the Swiss).
- Francuz (Frenchman) or klucz francuski is a Monkey wrench.
- Finka (Finnish-woman) is a kind of knife.
- Polka (Polish-woman) is a dance
- Węgierka (Hungarian-woman) is a type of a plum
- Hiszpanka (Spanish woman) is a name used also for Spanish flu
- Chińczyk (Chinese man) is also a name for a game
No, it's Nominative. Somehow this word is kinda problematic here. I'd say that "Kelner!" is not very polite (but is "Waiter!" polite? I really don't know), but on the other hand using Vocative "Kelnerze!" sounds very strange, and "Panie kelnerze!" absurdly polite. I believe that "Panie kelner!" may be used sometimes, regardless of its weird grammar.
Frankly, I would personally avoid it at all. For native Polish speakers there are ways to avoid addressing people in any way - mostly when you have no clue whether you should be informal (ty) or formal (pan/pani). Like rephrasing your message so "you" is not its subject ;) But if I had to address the waiter directly, I'd use "Proszę pana" and other "pan" forms.