I’m having a hard time with the construction “O’n i’n meddwl i ti ddweud” for the English “I thought you said that you wanted to go out.” I have no such problem with the “i ti” for “I want you to…”
Can someone explain this to me simply? I’m not sure why I can’t wrap my head around it, but my gut is always to go with dwedaist ti or even dy fod ti. Is this a common construction with words other than eisiau/moyn and meddwl?
Diolch o flaen llaw.
Hmm, tricky question. But yeah, I think you’ll come across it in other structures - disgwyl, siwr, gobeithio come to mind immediately. In terms of explaining - once you’re past the ‘this is when you’d use it’, I suspect you’re not going to get much joy from ‘this is why the language works in this particular way’. If you’re clear about what the structure is for (I thought you said, or I was sure you asked, or I was expecting you to complain, etc etc) - then beyond that, I’m not sure what ‘explanation’ would actually be…
Would it help at all to think of it as being pretty similar to the ‘isio i ti’ structure?
Thanks - just going to keep plugging away at it. I think this popped up in the old courses, too, and it gave me a struggle there, too. I guess it’s a personal inclination to say/imagine I am hearing "I heard that you, which makes me automatically reach for bod.
The other words you listed will help me look for some more examples, pay more attention when listening to TV/radio. 
But don’t worry about it, because exposure will add it to your toolkit eventually, if necessary… 
Still thinking about it 5 minutes later, and I guess there are two parts that are confusing 1) it refers to the past tense and 2) when I think of “dw i isho i ti” or “dw i’n gobeithio i ti” I translate it as “I want for you to” or “I hope for you to.” I’m guessing that’s wrong, lol. With the example from challenge 14, it moves away from the ability to use “for you” hence does not compute for me.
Well - it’s not ‘wrong’, as in ‘that is the sense you’re communicating’ - on those lines, ‘o’n i’n meddwl i ti’ would be something like ‘I was thinking for you to say’.
But really, it’s same old same old - languages don’t match to each other, and as soon as you’re past the basic stuff, you need to get better and better at letting go of our own language and swimming along (doggy paddle or however!) in the new stuff…