"What do you think of Dewi Lingo?"
Translation:Beth wyt ti'n feddwl o Dewi Lingo?
I am also puzzled. If "meddwl" was a verb that did not have to be followed by a pronoun, I could see where "ei feddwl o" might come from if the English version used the pronoun "him", but this sentence uses a name, not "him".
As far as I know, "meddwl o" and "meddwl am" are used for "think of" / "think about". "meddwl o" in this case, and I can't see how "ei" would be needed in the first place, even if it is then left out.
Meddwl (thinking) needs an object in Welsh when used with questions such as Beth? and Pwy?. This is given by the 'object complement' pronoun ei in the pattern:
- Beth wyt ti'n ei feddwl ...?
The ei causes a soft mutation of the meddwl.
In the colloquial language, the object complement pronoun ei is usually dropped, but the mutation it causes remains:
- Beth wyt ti feddwl? - What do you think?
Similarly with gwneud (making, doing):
- Beth wyt ti'n (ei) wneud? - What are you doing?
(There are various other verbs that need this kind of object, too, but it is the sort of thing that quite often gets dropped in the colloquial registers of the language. It seems to have stuck with gwneud and meddwl in particular, though, and with a few others.)