There's the expression - talking the hind legs off a donkey, which is under discussion on a couple of English language forums. On English Stack Exchange, someone has suggested that it comes from Irish and literally it would be - making a donkey sit down on it's rear end. Another person on the same forum disputes this, saying that they haven't found any trace of it - in Dinneen or anywhere else. Does any one know of an expression in Irish that connects the idea of talking a lot and donkeys? I always had the impression that not only did it mean talking for a long time, but ironically giving the idea that the person doing the talking could finally persuade you into believing anything. In Provence there's the expression - prendre le temps pour tuer l'âne à coups de figues - taking the time to kill the donkey by throwing figs at it - meaning wasting your time doing something that's impossible or nonsensical.
Of course there's the toilet - tig an asail, which must have started out as a joke that's now become an everyday expression.

http://english.stackexchange.com/questi ... f-a-donkey

For me that phrase means that someone just keeps on talking, whether or not you want to listen. I wouldn't associate it with being persuasive, as you generally want to get away from someone who'd talk the hind leg off a donkey. I was told that a donkey's hind legs are very strong, and to take or "talk" them off would require a lot of effort. I don't know though.

I don't think the phrase came from Irish, as in most phrases I've heard "asal" would've been translated as "ass", and there's probably a pun in there between "talking" and "taking".

And more to the point, what did the donkey ever do to you that you'd want to go i dtigh an asail