I'm a native (American English) speaker and I've noticed that this is a weird feature of my idiolect. Here is a direct quote:
To the person for whom I spilled apple cider, if you're watching this, I'm sorry.
I should add that this was definitely informal speech. Why did I say that, though, and not "To the person whose apple cider I spilled…" which is a lot cleaner and less clunky? Is there anyone else on this forum whose speech/language use features this quirk (or as I would more often say, "…for whom this is a part of your idiolect?") I don't know where it came from and my memory can't trace it back to anything in particular that may have influenced this. Are there any linguistic articles/studies/information in general about this, or am I just… weird? (Generally I've noticed that my brain defaults to really clunky sentence structures especially in informal speech, of which this is only one example.)
Edit because I can't resist including this connection: For those of you who are familiar with German, this is basically "Der Dativ ist dem Genitiv sein Tod" but in English. I wonder what kinds of unsavory words Bastian Sick would have to say to me.
Edit (again): I realize that instead of "Is there anyone else on this forum for whom this is a part of your idiolect?" I could say "…for whom this is an idiolect feature" which is much cleaner and makes more sense (here the preposition stranded version kind of works as well: "…who(m) this is an idiolect feature for" but I wouldn't say it like that.) The very clunky way that I originally worded it is an authentic representation of how I would likely actually say the sentence, though (especially if I'm not careful!)
Best Answer
And the third version
Consider:
If we know the person we can say, “I dug the garden for you but you have not paid me yet.” In which “for you” modifies “dug” and is thus adverbial.
Or, If we don’t know them, then we can post the notice: “To the person for whom I dug the garden, you haven’t paid me yet.” In which “for whom I dug the garden” modifies “person” and is thus adjectival.
Or “To the person whose garden I dug, you haven’t paid me yet.” (“whose garden I dug” – adjectival.)
You can also say, “I dug your garden, but you haven’t paid me yet”
Yet by comparing it with your example, you can see that “for you” = “to your benefit” or “at your request” or “on your behalf” – it is hard to see how spilling someone’s drink and then regretting it fits into this category.
It seems to me that this is a form of misspeaking similar to a malapropism, modegreen, or eggcorn, etc., all of which sound perfectly normal to the speaker.
The phrase seems to have stuck in your mind and nobody, out of politeness or lack of interest, has bothered to correct you.
The amazing thing is that you know what you should be saying, yet persist with the wrong version.
I don’t think it is the German that you are learning that is causing the difficulty as German addresses the sentences as in English “für die/den/das” and “deren/dessen”.