This is one of the many entries in this book which made we wonder whether Cassidy and his supporters are completely unhinged. I mean, how stupid would you need to be to believe that the word ditch (as in ‘she ditched him’) comes from the supposed Irish phrase de áit? Cassidy doesn’t give any examples of this phrase in use. It would be hard to do so, because the phrase isn’t in use and never has been.
The two words exist independently, of course. De means from or ‘off of’, ‘from the surface of’ (bhain siad an pictiúr den bhalla – they took the picture off of the wall), while áit means place. And occasionally they occur together in phrases like an phrochlais sin de áit (that dump of a place) or taobh amuigh de áit (outside of a place) but in the standard language, this would usually become d’áit and it isn’t anything to do with displacing or dislodging or dumping in these cases. If you want to say that someone displaced something or put it out of its place you would use as áit, not de áit: cuireadh na brící as áit nuair a thit an scafall orthu (the bricks were dislodged when the scaffolding fell on them).
And anyway, with the dubious exception of ‘defenestrate’ (i.e. throw out of the window, which is hardly a common term, even in Prague) most words which mean ‘to get rid of’ describe the destination, not the origin of the object. You don’t untable something, but you can certainly floor someone. You don’t outhand something but you certainly bin it. You don’t unrelationship someone (actually, with Facebook, maybe you do these days!) but you certainly dump them. And even if you did, would you ‘from a place’ someone or something when you dump it, rather than when you dislodge it? From a place isn’t very informative! Obviously, if you move something they were in a different place before! So, de áit is pretty much impossible, for a variety of reasons.
The English ditch, on the other hand, is very likely and incredibly, blindingly obvious. A ditch, meaning a kind of trench at the side of the road (or sometimes the bank beside the trench in Ireland), comes from the Old English word dic. And in the old days, when you had some rubbish you dumped it in the ditch, or ditched it. In time, this became a general term for discarding or dumping.
This isn’t rocket science. I do have academic degrees but you don’t need a degree to work out that Cassidy’s claim is nonsense. All you need is reasonable literacy skills, access to the internet and an open and sensible mind. Which is why I find it really strange that so many people are prepared to support a book that contains so many transparent stupidities like this.