Felipa

I must confess that there were high-seas in the Sruth na Maoile of my mind when writing of shanty and I did not consider the Gaidhlic pronounciations. If shanty is from sean and teach then I would consider Scotland the place where it happened. The reason for pubs (and everyone's house in normal usage) being called tigh Sheáin or tigh Mháirtín is that these were mostly used in the dative case due to people traveling to or from them or speaking of something in them etc. All these situations require simple prepositions which in turn required the dative. The same phenomenon of old datives being used as nominatives is seen in placenames (for the same reasons) - therefore Aird instead of Ard etc. This usage of tigh doesn't occur where the adjective sean- could be placed before it in Ireland except in Munster where the final g is pronounced without lenition.

Bothy - this is definitely of Gaidhlic and Gaeilge origin. The word both is in the earliest legal tracts and in the Old Irish glosses and means hut. (In one instance I remember it glosses the Latin for tabernacle.)   We usually use a diminutive form, bothán in modern Irish. I'm sure you still have both North of Malin Head as well, possibly spelt buth these days. Your word for shop could be related and then also the English booth, but I don't know if these have been investigated or not and I am uaigneach without my reference library on the continent at the moment.

I don't recall the etymology of both in Irish only (previous to the etymology of bothy < both) so I can't say if it is based on bó or not without a joyous reunion with Vendryes. However I don't think bothy in English comes from a compound of bó and taigh; rather from both or a diminutive of it. I remember that there is an abstract formation bothas in a 7th century legal text called Críth Gablach and that it meant servile tenancy or cottier status. The person of that status was a bothach.

Bó is however definitely the basis of bóthar.    Another very common word derived from bó is buachaill used in the modern language for a boy. It originally meant a herdsman and we still use it as a verb "ag buachailleacht" to which is added (superfluously among etymologist farmers) "na mbó". This is a bit like saying Oileán Í of Iona when Í already means island (and is cognate of it and isle in English, ile in French etc. - inis a purely native Irish word for island).

BTW, iona is Hebrew for dove and Colm is Irish for dove, so when did it first get called Iona?