For example, Old Irish borrowed a fair number of words from British many of which in turn had been borrowed by the Ancient Brits from Latin during the Roman Occupation, or later in connection with christianity. The loans to OI then passed down to the modern three Gaelic languages, while the British word descended to Welsh/Cornish/Breton. So for example, the Latin word vespera 'evening' was borrowed by British and comes through in Welsh as gosber, Breton gousper (mainly in connection with the 'vespers' evening service), and was passed on to OI giving e.g. Scots Gaelic feasgar, Manx fastar which are the normal everyday words for 'evening'. Question : which of these words are cognates?
If a word common to all the modern Celtic languages could be shown to go back to Common Celtic, but nevertheless could then be shown to have been an early loan to CC (for example from Germanic), would those words be technically cognates or loans?
The English word 'potato' (from wherever) appears to have been borrowed independently into five or the six modern Celtic langs. (and probably independently in at least two Mod. Irish dialects). Are these words 'cognates' with English 'potato' or with one another, or neither?
In the last case I'd say definitely 'no', apart from anything else the sound changes are pretty random. But in the earlier examples there are usually quite predictable sound changes, e.g. Latin /-kt-/ > British /-xt-/ > OI /-xt-/ > SG /-xk/, and on a different branch > Welsh /-jT/ > Breton /-jz/.
To add to the confusion, a British word might be borrowed into Irish at two different periods, and either undergo a whole list of Irish sound changes (if borrowed early) or a parallel but different list of British developments (if borrowed later), and sometimes the same word went through both routes given two different words in Irish. How do you deal with that when compiling a cognates list?
Or a borrowing from the other branch can sit alongside the same word that's been inherited down the regular path.
So you see, I'm a bit confused ...


