We can receive most interrogative pronouns by adding case suffixes to ma (masse, manen, man, etc.), but there is still one word missing: A word for why.
I thought that we could use the word casta (reason), to formulate a sentence, but I'm not shure how this sentence should look like. I thought about a combination with the impersonal relative pronoun with the ablative suffix, like: Mana i casta yallo ... (what is the reason "wherefrom"...). Does that work? It sounds pretty wrong in English, but would it work in Quenya?