When I need a character with a cultural background that the author is not familiar with, the name of the character always makes me difficult. Every culture has its own naming habits, not only the format of first name and last name, but also the special regulations due to local culture and laws. There is even a variant of a name (like when a Spanish family wants to name a child Carl, the child will eventually be called Carlos, Carl's Spanish variant). Using search engines is a good way, But I'm afraid I'll fall into a trap whose name is too common or even clich Ă© D (for example, in an article, the Germans are always called Hans, the French are always called Louis, and the Russians are always called Mikhail). How did you deal with it?
Personally, I tend to write characters from cultures I'm familiar with. So I'm pretty confident that, if I need a Japanese name, I can come up with something suitable. When I'm writing characters from other cultures, I do try to use sources of names like sportspeople, so I don't end up with Spanish characters called Juan Valdez or French characters called Pierre Dupont. Footballers and tennis players, for example, have a wide enough selection of international names to give you a good idea. For Commonwealth countries, cricketers are great.
If it's important enough that the character come from x culture, then it is important and worthwhile that you acquire some familiarity with x culture. Read some history and literature, watch movies, etc.
I look up historical censuses. Or I'll just steal names from old newspapers. There are plenty of them online. Because you can consider people of another time to be another culture, even if they're from the area you live in now. They're certainly removed from us. The point of it is that names change with time and you want one period appropriate too.
What's wrong with: Said King Arthur to his knights, "Sir Kyle, Sir Ethan, Sir Jude and Sir Josh, wilt thou slay the dragon and save Lady Billie?"
It's admirable that you want to show respect for foreign cultures rather than just name your characters Fritz von Hamburg or Mustafa ibn Ali. I started to think what I would do if I needed a character from, say, Tonga. Maybe I would start with a web search like common tongan names tonga frequent surnames Then I would try to find out if Tonga has some kind of a government statistics website in English. Maybe they have some data on, say, last year's most frequent given names. To find out about their naming standard, I would probably ask on a language learning forum such as hinative.com, or try to find another language learning or travel or cultural forum, maybe by doing a web search tonga forum Of course, you can also ask about common names on such a forum. It's my impression that many people enjoy explaining such things to foreigners. As concerns the variations of a name in the spoken languages (such as a Russian woman with the official name Viktoriya being colloquially called Vika, Vichka or Vik depending on the situation and the relation to the speaker), I would rather not attempt to catch such fine nuances.
David Cronenberg just used names of Canadian motorcycle racers. At least in Videodrome and The Fly. Hence weird names like Seth Brundle and Max Renn. But hey, unless you're really into motorcycle racing or Canadian (or probably both) you woudn't recognize any of them.
First thing that springs to mind with Tonga is rugby. Therefore, I personally would start here: https://en.wikipedia.org/wiki/Tonga_national_rugby_union_team#Players
You could always use Biblical apostles—like John, Paul, George and Ringo. Sorry, just a little joke.