I agree with henddraig that you might need to wait for Aran to come back from the Eisteddfod (which will be next week now) to get a definitive answer.
But I wonder if it’s something to do with prepositions? I’ve got a handy little book called “Pa Arddodiad”, which lays out a number of verbs and the prepositions that they take (which is always one of the hardest things to get to grips with a new language, as they often don’t map across from one language to another). It gives me these different options, with my own suggested translations in square brackets:
- gofyn am (rywbeth) [to ask for (something)]
- gofyn (rhywbeth) gan (rywun) [to ask (for something) from (someone)]
- gofyn i (rywun wneud rhywbeth) [to ask (someone to do something)}
- gofyn i (rywun) am (rywun/rywbeth) [to ask (someone) about (something/something)
- gofyn dros (rywun) [to ask after (someone)
But after I typed all this out I realised that none of these uses ‘wrth’. So I did a bit of Googling, and found this:
Hope some of this helps! It might be too much information, though.