This is one of the few words in Cassidy’s crazy book which has the ring of truth about it, the idea that shanty derives from Irish seanteach or seantigh, which mean ‘old house’. Unsurprisingly, some of the dictionaries themselves mention the possibility of a connection with seanteach and it is widely believed in Ireland that shanty and seanteach are the same. This tells us something quite important – where there is a genuine similarity, people picked up on it and wrote about it long before Cassidy had his brainwave. In the vast majority of the entries in Cassidy’s drossary, the supposed ‘original’ phrase doesn’t exist (béal ónna, sách úr, éamh call, seinnt-theach) and only lunatics like Cassidy make a connection between a real phrase in one language and a made-up phrase in another.
So, on the face of it, seanteach looks like a pretty strong candidate. But is it?
Firstly, there is another good candidate, the Canadian French chantier, meaning a log cabin used by lumberjacks. Chantier is pronounced shantee-eh.
There is also the problem that Irish has a number of words for hut. I think most native speakers would use words like cró or bothán instead of seanteach. There is a word seantán, defined as ‘shanty, shack’ in the dictionary (Ó Dónaill) but this is probably of modern origin and based on shanty, as it is a diminutive and there seems to be no word seant in the Irish language which could be its origin.
However, the most compelling reason for rejecting seanteach is that a shanty is by nature not an old house. A shanty is temporary, new and thrown-together.
In other words, this is not a stupid claim. It looks believable. However, it is very, very unlikely that it is correct.