Darth ain't Dutch
Sorry, I just have to vent... kindly indulge me a moment.
It seems whenever a discussion is held about the origins of the name "Darth Vader" someone inevitably claims it means "dark father" in Dutch.
Now it may be possible that George Lucas had "dark father" in mind when he created the name (I for one doubt it - I still believe he didn't come up with the father angle until some time after ANH), but if he did, he probably only changed some letters to distort it and make it sound more GFFA, a technique he has used with a lot of names since (Zett Jukassa for Jett Lucas comes to mind).
ANYWAY, my point is: Nobody who claims the origins of the name are Dutch (and why the hell should they be?) ever seems to bother digging out an English-Dutch dictionary and actually try and verify those claims.
Well, I just did. Three different online dictionaries, in fact, just to be sure.
The good news:
"Vader" is indeed a Dutch word meaning "father".
(It is however pronounced a lot differently, more like "faah-der", not like "vay-der", but that's kinda beside the point and not really part of my argument.)
The bad news:
"darth" is not a word in the Dutch language. (I'm not 100% certain, but I'm fairly sure Dutch doesn't even have the English "th" sound.)
According to the dictionary, some Dutch words for "dark" are "somber", "duister", (those two being probably the closest to "dark" in a Darth Vader sense, meaning also "gloomy"/"ominous"/"sinister"/"scary"😉, "donker" (also pretty close in meaning, but more likely to mean "not light"😉 and "onverlicht" (meaning simply "unlit"😉.
I hope this'll finally put at least one part of the "Vader" origin debate to rest.
To repeat, it's well within the realm of the possible that Lucas meant for the name to signify "dark father", but claims that the name is derived from Dutch are nonsense.
Thanks for listening. I'll get off the soapbox now.
(Any Dutch people out there, please feel free to correct or confirm me as Dutch is not my native language.)